PHOENIX (AP) — A Drug Enforcement Administration special agent who was shot and killed by an Amtrak train passenger in Arizona was identified Tuesday.

Special Agent Mike Garbo was the agent slain during an inspection in a train car stopped in Tucson, according to two people familiar with the matter but who could not discuss the matter publicly and spoke to The Associated Press on condition of anonymity.

The DEA is expected to formally identify him later today.

Members of the law enforcement community took to social media to describe Garbo as an excellent police officer who started out in Nashville, Tennessee. The Metropolitan Nashville Police Department said someone with the same name worked there between 1993 and 2005 but could not confirm he was the deceased agent.

A second agent and a Tucson police officer were wounded in the Monday morning shooting. The agent was listed in critical condition while the officer was in stable condition. Authorities have not released their identities.

The Sunset Limited, Train 2, was carrying 137 passengers and 11 crew members traveling from Los Angeles to New Orleans, and arrived at the downtown Tucson station at 7:40 am, said Jason Abrams, an Amtrak spokesman.

The shooting occurred about 20 minutes later and sent panicked passengers running. A regional task force of DEA agents and Tucson police officers had boarded one of the cars to do a check for illegal money, weapons and drugs.

Officers were in the middle of detaining a man on the upper level of the double-decker car when a second man pulled out a handgun and began firing. He exchanged several rounds with police and then barricaded himself in a bathroom on the lower level, according to Tucson Police Chief Chris Magnus.

He was later found dead inside.

The other suspect was arrested. Authorities have not said what charges he faces or his relationship to the slain suspect.

There were no other injuries among the train's passengers or crew.

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Associated Press writer Mike Balsamo in Washington contributed to this report.