By RYAN FOLEY, Associated Press

MONTEZUMA, Iowa (AP) — Authorities said on Tuesday that they have charged a man living in the U.S. illegally with murder in the death of an Iowa college student who disappeared a month ago while jogging in a rural area.

Iowa Division of Criminal Investigation Special Agent Rick Rahn said that Cristhian Bahena Rivera, 24, was charged with murder in the death of Mollie Tibbetts.

Investigators say they used surveillance video in tracking down Rivera. The video showed Tibbetts, 20, jogging in a rural area near her hometown of Brooklyn as well as Rivera's car.

Police announced the charge at a press conference just hours after they found what they believe to be the body of Tibbetts in a field covered with corn stalks.

Tibbetts was last seen July 18 in Brooklyn, a rural town of about 1,400 people, as she took a routine evening jog. It's unclear whether she returned to the home where she was dog-sitting for her boyfriend and her boyfriend's brother, who have said they were both out of town . She was reported missing by her family the next day, after she didn't show up for work at a day camp for children.

Tibbetts' disappearance set off a massive search involving dozens of officers from the FBI, as well as state and local agencies. They focused much of their efforts in and around Brooklyn, searching farm fields, ponds and homes. Investigators asked anyone who was around five locations , including a car wash, a truck stop and a farm south of town, to report if they saw anything suspicious on July 18.

Last week, Vice President Mike Pence met privately with the Tibbetts family during a visit to Iowa and told them that "you're on the hearts of every American."

At Brooklyn City Hall, city clerk Sheri Sharer said Tuesday was a sad day for the town.

"It never crossed our mind that she wouldn't come home safe," she said.

Willey's group has been publicizing a reward fund that raised around $400,000 for any tip that led to Tibbetts' safe return. He said the fund, which included more than 220 donations from individuals, will now likely be used for any information that helps police catch anyone responsible for her death.

"Once they catch their breath, this will turn into a weapon going the other direction, to catch the person who did it," he said.

Tibbetts, a psychology major, would have started her junior year this week in Iowa City, about 50 miles (80 kilometers) east of Brooklyn. She was staying with her longtime boyfriend and working while home from school over the summer.