A federal agent died and two other law enforcement officers were injured in a shooting on an Amtrak train at a station Monday morning in Tucson, Arizona.

Members of a regional narcotics "alliance" of local and federal authorities were conducting a routine check on a stationary train when a man opened fire, Tucson Police Chief Chris Magnus said Monday. Authorities were detaining another man on the train's upper deck when the shooter pulled out a handgun, he said.