“The gentleman had the gun with him and somehow he accidentally discharged the gun,” Oro Valley Police Sgt. Amy Graham told the Tucson Weekly. “The other employees could see him with it and separately he fell to the ground.”

ABC-affiliated KGUN reports the man has been identified as 40-year-old Noel Watts. When officers arrived at the scene, they found Watts unconscious and heavily bleeding from a wound to his leg. Paramedics applied a tourniquet and performed CPR on the man for more than 30 minutes, but were unable to save him.

Investigators are interviewing the victim’s co-workers to determine why he brought the firearm to the job, though Graham indicated the police believe the shooting was accidental in nature.

According to CBS-affiliated KOLD-TV, the high school was put on lockdown immediately after the gunshot was reported. The incident occurred on the west side of the school’s campus, and registration was occurring on the east side of the campus, meaning several staff members were present. A statement from the high school said no staff or students were in danger.

The statement went on to say that Arizona law and the school district’s policy prohibits anyone except peace officers or other authorized personnel from carrying firearms on school grounds.