By Eric Levenson, David Shortell and Brian Todd, CNN

(CNN) -- [BREAKING NEWS UPDATE 11:35 a.m.]

One person is dead after an armed student shot two other students at Great Mills High School in Maryland on Tuesday morning, according to St. Mary's County Sheriff Tim Cameron.

Cameron said the school resource officer engaged the shooter and ended the threat, and the shooter was pronounced dead. A male student is in stable condition and a female student is in critical condition, he said.

The school resource officer fired a round at the shooter, and the shooter fired a round as well, but the officer was not injured.

[ORIGINAL STORY, POSTED 11:02 a.m.]

(CNN) Three people were injured in a shooting at Great Mills High School in Maryland on Tuesday morning, according to Andrew Ponti, an official with the St. Mary's County public information office.

There are no fatalities reported at this time, Ponti said. It's unclear if the shooter is among the injured, he said.

The St. Mary's County Sheriff's Office responded to the shooting and said the event has been contained. The school was on lockdown for a brief time, and students were evacuated from Great Mills High School to a reunification center at a nearby high school, the school system said.

'I'm still a little shaken up'

Jonathan Freese, a student at Great Mills, called CNN from his cell phone as he was in lockdown in math class. Police were going through classrooms to clear the school, Freese said.

"I'm still a little shaken up," he said.

Freese said the school had held drills a couple of times for this kind of situation.

"I didn't really expect for this to happen. I do always feel safe, though, because they always have police at the school," he said.

A spokesman for the FBI's Baltimore field office said its agents are on the scene of the incident. Special agents from the ATF's Baltimore office are also at the school, that office tweeted.

Great Mills High School has an enrollment of just over 1,500 students, about 56% of them minority students. The school has a four-year graduation rate of 91%, according to the school's 2015-16 improvement plan.

Al Murray shot video of police responding to the shooting at the high school Tuesday. He says he saw at least one officer run into the building with a shotgun or rifle.

17th school shooting this year

According to CNN's research, there have been 16 confirmed school shootings this year in the United States prior to Tuesday.

Last week, students at Great Mills High School walked out of class as part of a student-led protest against school violence in the wake of the mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida.

Several students from Stoneman Douglas tweeted about the Great Mills school shooting on Tuesday, offering their thoughts and calling for an end to gun violence in schools.

"Less than a WEEK ago Great Mills High School students walked out with us to protest gun violence... now they're experiencing it for themselves," said Jaclyn Corin, a student fighting for gun reform. "The state of our country is disgusting - I'm so sorry, Great Mills."

"We are Here for you, students of Great Mills," student activist Emma Gonzalez tweeted. "together we can stop this from ever happening again."

"The words School & Shooting should not be next to each other. Headlines like this should not have to be typed up every week. All of these incidents have one thing in common. My thoughts are with Maryland right now," tweeted student activist Adam Alhanti.

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