By Jason Hanna, Ralph Ellis and Steve Visser CNN

(CNN) -- The killing of two Iowa police officers Wednesday brought the number of US law enforcement officers shot to death this year to at least 51 -- well ahead of last year's 12-month total, according to the National Law Enforcement Officers Memorial Fund.

The most recent shootings, in the Des Moines area, appear to be ambush killings, authorities said. An officer from the Urbandale police was found dead in his car around 1 a.m. and a Des Moines officer was discovered dead at an intersection about 20 minutes later. Police later took a suspect into custody.

The 2016 shootings have spanned the nation, from California to Massachusetts, and they've exceeded the number of firearms-related police deaths in all of 2015. According to the fund, firearms were responsible for 41 of 123 officer fatalities in 2015.

The decade's highest total came in 2011, with 73 officers shot dead.

This year's shooting deaths include a 28-year-old officer on her first day on the job and a 65-year-old sheriff's corporal who was about to retire. Here's a look at all the officers shot and killed in the line of duty this year, as of November 2:

ALASKA

SGT. ALLEN BRANDT
Brandt, an 11-year veteran of the Fairbanks Police Department, was shot multiple times October 16 while responding to reports of gunfire. He was wearing body armor but was struck by bullets in a leg and shrapnel in an eye. He died October 28 of complications experienced during surgery. After the shooting, the father of four had been well enough to speak at a community council meeting, saying he had predicted to his family he would be shot. The suspect, who fled in Brandt's patrol car, was arrested.

ARIZONA

OFFICER DAVID GLASSER
Phoenix police Officer Glasser, 35, was responding to a report that a man was stealing guns from his father's home when he was shot on May 18, CNN affiliate KTVK-TV reported, citing police.

Glasser died a day later.

He and other officers had arrived outside the home in Phoenix's Laveen area. The caller's son was in a van when Glasser and his partner parked their squad car but got out of the van and shot Glasser, KTVK reported. Other officers returned fire, killing the gunman.

Glasser was survived by a wife and two children, KNXV reported.

ARKANSAS

SHERIFF'S CPL. BILL COOPER
The 65-year-old Sebastian County sheriff's deputy was on the verge of retirement when he and other officers responded to a 911 call at a manufactured home August 10 in rural western Arkansas, between Greenwood and Midland.

The caller said a man had pulled a gun on his father. When deputies and officers arrived, the son, wearing body armor, fired a rifle repeatedly, killing Cooper and injuring another officer and a police dog, authorities said.

The gunman eventually surrendered and was arrested, police said.

CALIFORNIA

OFFICER JONATHAN DeGUZMAN
DeGuzman, 43, of the San Diego Police Department, and another officer were shot as they tried to stop someone in the city's Southcrest section on the night of June 28, police said.

A fellow officer arrived and rushed DeGuzman to a hospital, where he died. His wounded colleague survived. Police arrested a 52-year-old man in connection with the shootings.

SGT. STEVE OWEN
Owen, 53, of the Los Angeles County Sheriff's Department died October 5 after a suspect shot him while he was responding to a residential burglary. He was a 29-year department veteran. The suspect was apprehended.

OFFICERS JOSE GILBERT VEGA AND LESLEY ZEREBNY
Vega, 63, and Zerebny, 27, both of the Palm Springs police, were shot and killed October 8 while responding to a domestic disturbance. The officers were trying to negotiate with a distraught man who was inside a residence when he fired through the closed front door.

The suspect was arrested after barricading himself in the house for 12 hours.

Vega was a 35-year veteran nearing retirement, and Zerebny has just returned to work from maternity leave.

DEPUTY SHERIFF JACK HOPKINS
Hopkins of the Modoc County Sheriff's Office was shot and killed October 19 while responding to a disturbance report. A suspect was arrested by other officers.

COLORADO

SHERIFF'S DEPUTY DEREK GEER
Geer, 40, of the Mesa County Sheriff's Department died February 10, two days after he was shot as he tried to detain a man in Grand Junction.

The deputy had responded to a report of a person walking past an office building with a handgun under his armpit, near railroad tracks south of the Interstate 70 business loop, police said. Geer saw someone matching the person's description and tried to stop him, even Tasering him, but the person shot Geer, police said. A suspect later was arrested.

Geer was an organ donor. In May, CNN published a story about a patient who received Geer's heart.

SHERIFF'S CPL. NATE CARRIGAN
Carrigan, 35, of the Park County Sheriff's Department, was fatally shot while he and two other deputies were trying to serve an eviction notice near Bailey on February 24.

The gunman -- a man who was being evicted -- also shot the other two deputies, wounding them. The deputies returned fire and the man was killed, police said. Carrigan was a 13-year veteran in the department.

GEORGIA

MAJ. GREG BARNEY
Barney, of the Riverdale Police Department, was helping police in Clayton execute a drug-related warrant at an apartment when he was fatally shot on February 11, police said.

Barney was a 25-year veteran of the department and had a wife and two children, CNN affiliate WSB reported.

OFFICER TIM SMITH
The Eastman, Georgia, policeman was responding to a call about a suspicious person when he encountered a man who shot him and fled the scene. Smith died at an area hospital.

Smight died just two days before his 31st birthday.

He left behind a fiancee, two sons, a 5-month-old daughter and a stepson, his fiancee told CNN.

INDIANA

SHERIFF'S DEPUTY CARL KOONTZ
Howard County sheriff's Deputy Carl A. Koontz, 27, was shot and killed March 20 in a shootout at a Russiaville trailer park while trying to serve a warrant for a man accused of failing to appear in court on charges of illegally possessing a syringe, police said.

One of Koontz's colleagues also was injured in the shooting. The shooter -- the man who was named in the warrant -- then fatally shot himself in the head, police said. Koontz, a former Marine, had nearly three years on the job.

KANSAS

DETECTIVE BRAD LANCASTER
The Kansas City, Kansas, detective was shot and killed May 9 while responding to a call of a suspicious person near a casino.

The gunman fled in the detective's vehicle and stole two more vehicles before being arrested, police said.

CAPT. ROBERT DAVID MELTON
The Kansas City, Kansas, officer was shot and killed on July 19 while chasing people who'd allegedly been involved in a drive-by shooting, police said.

Melton, 46, was his department's second officer to be shot dead in the line of duty after Lancaster (above).

LOUISIANA

SHERIFF'S DEPUTY DAVID F. MICHEL JR.
The Jefferson Parish sheriff's deputy was shot dead on June 22 during a confrontation with a man he had approached on the street, authorities said.

SHERIFF'S DEPUTY BRAD GARAFOLA
Garafola, 45, of the East Baton Rouge Parish Sheriff's Office, was one of three Louisiana law enforcement officers shot dead -- and one of six shot in total -- on July 17 by Gavin Long in Baton Rouge, police said.

Long shot the officers after posting a YouTube video in which he spoke about recent protests and officer-involved shootings, and said that victims of bullying needed to resort to bloodshed.

The officers' deaths came nearly two weeks after a police officer shot and killed Alton Sterling, a Baton Rouge resident. That death, as well as a July 6 shooting of a man by police in Minnesota, kicked off days of national turmoil that included a gunman shooting and killing five police officers in Dallas on July 7.

OFFICER MATTHEW GERALD
Gerald, 41, of the Baton Rogue Police Department, was one of three Louisiana law enforcement officers shot dead -- and one of six shot in total -- on July 17 by Gavin Long in Baton Rouge, police said.

(See entry for sheriff's Deputy Brad Garafola).

CPL. MONTRELL JACKSON
Jackson, 32, of the Baton Rouge Police Department, was one of three Louisiana law enforcement officers shot dead -- and one of six shot in total -- on July 17 by Gavin Long in Baton Rouge, police said.

(See entry for sheriff's Deputy Brad Garafola).

MARYLAND

SHERIFF'S DEPUTY PATRICK DAILEY
Dailey, of the Harford County Sheriff's Office, was one of two deputies fatally shot at or near a restaurant in Abingdon on February 10.

Dailey was called to a Panera Bread restaurant to investigate a man, but as Dailey talked to him the man shot him in the head, police said. The man fled toward nearby apartments, where he shot and killed Deputy Mark Logsdon (below), police said. Other deputies shot the gunman, who was pronounced dead at the scene.

SHERIFF'S DEPUTY MARK LOGSDON
Logsdon, of the Harford County Sheriff's Office, was one of two deputies fatally shot at or near a restaurant in Abingdon on February 10. (See entry for Deputy Patrick Dailey, above.)

OFFICER JACAI COLSON
Colson and other Prince George's County police officers were in a shootout with a gunman who'd ambushed them outside their police station when Colson was shot and killed by mistake by a fellow officer on March 13, police said.

Colson, a 28-year-old undercover narcotics detective, was in plain clothes when he drove up to the station to find the gunfight under way. An officer shot him when he left his car to confront the gunman, police said.

MASSACHUSETTS

OFFICER RONALD TARENTINO JR.
The 42-year-old Auburn police officer was making a traffic stop in the early morning of May 22 when an occupant of the car fatally shot him and fled, police said.

MICHIGAN

COURT BAILIFF RONALD KIENZLE
Kienzle, 63, was one of two court bailiffs shot and killed July 11 in a courthouse in Berrien County by an inmate who had grabbed a deputy's gun outside a holding cell, police said.

SUPERVISING COURT BAILIFF JOSEPH ZANGARO
Zangaro, 61, was shot and killed along with Kienzle (above) on July 11 in a courthouse in Berrien County by an inmate who had grabbed a deputy's gun outside a holding cell, police said.

SGT. KENNETH STEIL
The Detroit police's Steil was wounded by a carjacking suspect with a sawed-off shotgun during a foot pursuit. Steil was expected to recover but developed a blood clot in the hospital and died two weeks later on September 17.

MISSISSIPPI

SPECIAL AGENT LEE TARTT
Tartt, 44, an agent with the Mississippi Bureau of Narcotics, was fatally shot on the morning of February 20 as he and other officers entered a home in Iuka, trying to end a six-hour standoff with a man inside, police said.

Police had been called there on a report of a domestic disturbance. Tartt was a 22-year veteran of law enforcement and had been with the Mississippi Bureau of Narcotics since 2000, CNN affiliate WREG in Memphis reported. He left a wife and two children.

MISSOURI

OFFICER BLAKE SNYDER
Snyder, 33, of the St. Louis police died October 6 while responding to a disturbance call. The officer walked up to a vehicle, and a suspect shot him once with a 9 mm pistol. His partner shot and wounded the suspect.

NEW MEXICO

OFFICER JOSE CHAVEZ
Chavez, 33, had just arrived to help an officer with a traffic stop in Hatch on August 12 when a passenger of the stopped vehicle exited and shot him, police said.

Chavez was taken to a hospital, where he had surgery before he was pronounced dead, police said. Three people were taken into custody.

OFFICER CLINT CORVINUS
Corvinus, a 4½ year veteran of the Alamogordo Police Department, was shot and killed September 2 as he and another officer pursued a wanted suspect on foot.

NORTH CAROLINA

OFFICER TIM BRACKEEN
Brackeen of the Shelby Police Department was shot September 10 while serving an arrest warrant. He died two days later at the hospital. The suspect was arrested a few days later in Rhode Island and charged with murder.

NORTH DAKOTA

OFFICER JASON MOSZER
Moszer, 33, of the Fargo Police Department was shot February 10 during a standoff that followed a report of a domestic disturbance at a home in Fargo, police said.

He died the next day. He was six-year veteran of the department and left a wife and two stepchildren, CNN affiliate WDAY-TV reported.

OHIO

OFFICER THOMAS COTTRELL
Cottrell was fatally shot behind the municipal building in the village of Danville on the night of January 17.

A suspect eventually was arrested. Minutes before Cottrell was killed, authorities said, the suspect's ex-girlfriend called them to say he had taken off with his weapons and was looking to kill an officer.

Cottrell was one of Danville's six police officers at the time of his death.

OFFICER STEVEN SMITH
Columbus police Officer Steven Smith was in an armored vehicle April 10, serving on a SWAT team that was trying to serve a warrant for alleged arson, when a man inside an apartment fired a shot into the vehicle, hitting Smith, CNN affiliate WCMH reported.

Smith, 54, died two days later. He left a wife and two adult children, WCMH reported.

The man suspected of shooting Smith was arrested.

OREGON

SGT. JASON GOODDING
Goodding and another officer were trying to arrest a wanted man on a street in the Pacific coast town of Seaside on February 5. The suspect resisted arrest and shot Goodding, who returned fire and hit him, police said.

Both Goodding, a 39-year-old Seaside police officer, and the suspect later died at a hospital.

PUERTO RICO

SGT. LUIS A. MELENDEZ-MALDONADO
Melendez-Maldonado of the Puerto Rico Police Department was shot and killed October 12 while he and other agents conducted a narcotics investigation.

SOUTH CAROLINA

OFFICER ALLEN LEE JACOBS
Greenville police Officer Allen Lee Jacobs, 28, was fatally shot on March 18 by a 17-year-old boy, police said.

Jacobs and at least one other officer were trying to interview the teen about a weapon purchase, but the teen ran. After the officers gave chase, the teen opened fire, hitting Jacobs, according to police. The teen eventually fatally shot himself, police said.

Jacobs left two sons and a wife who was pregnant.

TENNESSEE

SPECIAL AGENT DE'GREAUN FRAZIER
The Tennessee Bureau of Investigation agent was working undercover in Jackson, trying to buy illicit drugs from someone as they were sitting in a vehicle during in a sting operation, when the target pulled out a gun and tried to rob Frazier and an informant on August 9, authorities said.

Frazier, 35, was shot once and died at a hospital, the bureau said. The person accused of shooting him was arrested.

Frazier had joined the bureau only six months earlier. He was the first TBI officer ever killed in the line of duty.

OFFICER KENNY MOATS
The 32-year-old Maryville police officer and a partner went to a home to check a report of domestic violence involving someone with a gun on August 25. They parked their vehicle behind the house, found the alleged victim and helped that person to safety, police said.

The officers then took cover behind their vehicle to wait for help, but a man opened fire on them from a garage, hitting Moats in the neck, police said.

Other officers eventually arrested the shooter, police said. Moats died at a hospital.

TEXAS

OFFICER DAVID HOFER
Hofer was fatally shot in a park in Euless on March 1 while responding to a call of a suspicious person.

The suspect opened fire when Hofer and a partner arrived, police said.

SENIOR CPL. LORNE AHRENS
Ahrens, 48, of the Dallas Police Department was one of five law enforcement officers shot and killed by a gunman during a protest in Dallas on July 7.

The gunman, whom police eventually killed, had expressed that he was upset about recent police shootings, wanted to kill white people and white police officers, and "expressed anger for Black Lives Matter," Dallas police Chief David Brown said.

The protest was over two shootings earlier in the week in which officers fatally shot black civilians in Louisiana and Minnesota.

OFFICER MICHAEL KROL
Krol, 40, of the Dallas Police Department, was one of five law enforcement officers shot and killed by a gunman during a protest in Dallas on July 7. (See entry for Cpl. Lorne Ahrens).

SGT. MICHAEL SMITH
Smith, 55, of the Dallas Police Department, was one of five law enforcement officers shot and killed by a gunman during a protest in Dallas on July 7. (See entry for Cpl. Lorne Ahrens.)

OFFICER BRENT THOMPSON
Thompson, 43, a Dallas Area Rapid Transit officer, was one of five law enforcement officers shot and killed by a gunman during a protest in Dallas on July 7. (See entry for Cpl. Lorne Ahrens.) Thompson had gotten married less than two weeks earlier.

OFFICER PATRICK ZAMARRIPA
Zamarripa, 32, of the Dallas Police Department, was one of five law enforcement officers shot and killed by a gunman during a protest in Dallas on July 7. (See entry for Cpl. Lorne Ahrens.)

UTAH

OFFICER DOUGLAS BARNEY
Barney, 44, of the United Police Department of Greater Salt Lake was shot and killed while investigating a traffic accident January 17.

Barney and other officers had responded to the accident and then began to search for two people who had fled the scene. Barney found a suspect who shot the officer, police said. A shootout followed, leaving the gunman dead and another police officer injured, authorities said.

VIRGINIA

TROOPER CHAD P. DERMYER
Virginia State Police Trooper Chad Dermyer, 37, was participating in a training operation with other troopers at a Greyhound bus station in Richmond on March 31 when a man walked away from his luggage.

Dermyer approached the man, and after the two talked for a few seconds, the man pulled a gun from his waistband and fatally shot the trooper, police said.

Dermeyer and his colleagues had been training to look for suspicious activity. The shooter was not involved in the training program.

OFFICER ASHLEY GUINDON
On her first day on the job with Prince William County police, Guindon, 28, was shot and killed February 27 while responding to a report of domestic violence at a Woodbridge house, police said.

Two other officers were shot and injured. A man suspected of shooting them also is accused of killing his wife, whose body was found inside the home, police said.

Guindon had taken her oath of office the day earlier.

WISCONSIN

DEPUTY SHERIFF DAN GLAZE
Glaze, 33, of the Rusk County Sheriff's Office was shot and killed October 29 while investigating a suspicious vehicle. A suspect was taken into custody.

An earlier version of this story mistakenly included deceased Sgt. Craig Hutchinson of the Travis County Sheriff's Office in Texas.

CNN's Eliott C. McLaughlin contributed to this report.

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