A 60-year-old U.S. Army veteran is facing federal charges after he left an improvised explosive device on the campus of the Bay Pines VA Healthcare System, authorities said.

Mark Edward Allen, a St. Petersburg resident, was arrested Tuesday and charged with possession of unregistered explosive devices, records show. Investigators say a similar device was found at his apartment.

According to a federal criminal complaint, the Tampa Police bomb squad and the FBI responded on May 29 after a suspected explosive device was found on the sprawling campus at 10000 Bay Pines Boulevard. Authorities used X-ray technology to determine the device contained a 9-volt battery, electrical wires, an improvised initiator, an unknown powder and a clothespin switch.

Read more: Tampa Bay Times