DEA Agent Killed in Arizona Amtrak Shooting, 2 Other Officers Injured

A U.S. Drug Enforcement Administration special agent was killed in a shooting aboard an Amtrak train Monday that injured two other DEA officers.

The shooting took place Monday morning during a routine check for illegal items onboard in Tucson, Arizona, Chief Chris Magnus of the Tucson police said during a news conference, per The New York Times.

During a sweep of the train, which was stopped en route to New Orleans, a passenger opened fire on the three officers, one of whom was a city police officer working on a joint task force with the DEA, Magnus said.

While law enforcement detained one man on the upper level of the train during their sweep, another man began firing shots at the officers with his handgun. The assailant then barricaded himself in a bathroom, where he was later found dead, Magnus said, per The Associated Press. A second suspect is currently in custody.

Officials do not yet know why the gunmen opened fire on the train. Magnus said he wasn't sure if the officers found any illegal contraband during their sweep, per the Times.

The shooting left the city police officer injured in stable condition, while the second DEA agent is in critical condition, police told the Times, reporting that Magnus declined to disclose the names of the two injured officers.

Magnus called the shooting "horrific" on Twitter Monday, writing, "So proud of our @Tucson_Police officers whose heroic actions undoubtedly saved many lives."

The Tucson Police Department did not immediately respond to PEOPLE's request for comment.

The DEA confirmed the death of one of its officers in the shooting in a statement released on its website Monday. The name of the officer who was killed was not disclosed.

"Tragically, this morning, two DEA special agents and a DEA task force officer from the Tucson Police Department were shot during a law enforcement operation in Tucson, Arizona. One DEA special agent died as a result of injuries sustained during the shooting," Anne Milgram, DEA administrator, said. "A second DEA special agent is in critical condition. The DEA task force officer is in stable condition. We at the DEA are heartbroken by today's events and ask that you keep the families of the agents and task force officer in your thoughts and prayers."

No passengers or crew aboard the train were injured in the shooting, Amtrak told CNN. The train had been carrying 137 passengers and 11 crew members, all of whom were evacuated.

Amtrak did not immediately respond to PEOPLE's request for comment.

Evan Courtney, identified by the Times as a passenger on the train, shared an image of law enforcement embracing after the shooting on Twitter.

"I caught this heart breaking [sic] moment of two officers at the scene of the fatal shooting at Tucson Amtrak Station," Courtney wrote. "The @Tucson_Police @FBI have been superb. I'm safe due to their fast action."

Courtney told the Times he was getting coffee aboard the train when the shooting took place, describing his reaction as "fight or flight."

The incident is currently under investigation by the FBI, CNN reports.

Last week, an Amtrak train derailed in Montana, killing three people and injuring dozens of others.