The missing driver, Trent Michael Cook, 34, of Amarillo, was listed as "missing/endangered," the Amarillo Police Department said.
Police found the Rochester Armored Car Co. vehicle at around 7:50 a.m. today, after receiving a call that it was standing unoccupied, with the engine running.
Investigators are reviewing evidence and have not confirmed the circumstances of Cook's disappearance, according to the police department.
"Our first concern was with the welfare of the driver in this case, that's what we're looking at immediately, which is where is Trent Michael Cook?" Amarillo PD Sgt. Brent Barbee said. "Is he OK? Did he leave that vehicle because he wanted to? Did he leave that truck because somebody made him? One way or another our first and best bet is to talk to him."
Cook, who was not an armed employee, is 5 feet, 6 inches tall, weighs 165 pounds, and has blond hair and hazel eyes. He was last seen wearing a company uniform.
Investigators have not released details on the missing contents of the truck.