The police have made an arrest after a shooting occurred Monday aboard an Amtrak train in Tucson, Arizona, causing passengers to flee.

The shooting happened just shortly after 8 a.m. on a parked train at the station in downtown Tucson.

Train 2, was traveling from Los Angeles to New Orleans, and arrived at the Tucson station at approximately 7:40 am. Authorities said there were 137 passengers and 11 crew members on board at the time.

Amtrak has reported that no passenger or crew members were injured in the shooting, however,  an U.S. Drug Enforcement Administration agent was killed.

A second DEA agent was also shot and taken to the hospital. He is listed in critical condition. In the shooting, a Tucson police officer was also injured and taken to the hospital. That officer is listed in stable condition.

The first person detained is still in custody. An additional suspect was found deceased inside a bathroom on the train.