Amtrak train shooting that left 1 agent and 1 suspect dead result of marijuana bust, complaint shows

One Drug Enforcement Administration agent was killed and two other officers were injured in a shooting on an Amtrak train that was stopped in Tucson, Arizona, authorities said.

Agents boarded the train Monday morning to perform a routine check for illegal guns, money and drugs, after receiving a tip from Amtrak. Prior to boarding, they were given a list of names of the passengers on board -- two of whom were the suspects, Devonte Okeith Mathis and D.T., according to a criminal complaint against Mathis.

Once on the train, officers encountered Mathis and D.T. on the second level of the double-decker Amtrak car, Tucson police said.

The federal complaint filed Tuesday by FBI Special Agent David Neill states that an agent spotted Mathis and D.T. sitting in the same row, but on opposite sides of the aisle. The agent saw Mathis grab a blue backpack, a black drawstring bag and white plastic bag, and move them three or four rows away before returning to his seat. The agent asked Mathis if the bags were his, which he denied, the complaint says. The agent then removed the bags from the train to inspect them and found what he believed to be two packages of bulk marijuana.

The complaint states that agents then spoke to D.T. outside the train and "conducted a consensual K-0 sniff of several bags on the platform" of the Amtrak station, but at some point D.T. got back on the train. Once agents located the bulk marijuana in the bags, they tried to recontact D.T. on the upper level of the train. While attempting to contact D.T., DEA Group Supervisor Michael Garbo was shot and killed, the complaint says. Another agent and an officer were injured and taken to the hospital.

"Immediately upon shots being fired, law enforcement officers detained Mathis," the complaint says. "Additional law enforcement officers, including the TDP responded to the scene, and D.T. was subsequently shot and killed after firing a weapon at additional officers."

Garbo joined DEA in 2005 and "served honorably for more than 16 years as a Special Agent and Group Supervisor combatting criminal drug traffickers from the Nogales corridor to Kabul, Afghanistan," DEA Administrator Anne Milgram said in a statement.

"Group Supervisor Garbo's operational expertise, mentorship, and leadership were legendary in the Tucson community," Milgram said. "Across DEA, Group Supervisor Garbo was universally loved and respected for his leadership, and for his unrelenting passion to protect the safety of the American people. Above all else, he was a devoted and loving father and husband. DEA mourns the loss of our beloved colleague."

Another DEA special agent who suffered multiple gunshot wounds during the incident is in stable condition, DEA said Tuesday.

A Tucson police officer who was on the platform heard the gunfire and ran onto the train, at which point he was shot, police said. That officer is also in stable condition, police said.

A search warrant of the various bags taken from the suspects revealed 2.39 kilograms of raw marijuana, 50 packages of Gooberz (marijuana edibles) and other marijuana and cannabis products.

"The FBI reviewed the video surveillance, body camera footage and spoke with agents and TFOs from the DEA and Tucson Police Department," the complaint says.

There were no reports of injuries to the 137 passengers or 11 crew members, Amtrak said.

The train was en route from Los Angeles to New Orleans and arrived in Tucson at 7:40 a.m. local time, Amtrak said.

ABC News' Alex Stone, Nicholas Kerr and Luke Barr contributed to this report.