A military-style machine gun accidentally discharged at a gun club exhibition, killing an off-duty police officer who was working with the weapon, state police said Thursday.

A Gatling gun mounted on the back of a Hummer discharged Wednesday night during a demonstration, shooting Michael Kurty, 36, of Hollidaysburg, once in the head.

"We don't know if it malfunctioned, or if he was trying to clear it, but it appears to be an accidental shooting," state Trooper Jeff Petucci said.

More than 100 people were at the Hollidaysburg Sportsmens Club in Frankstown Township, about 90 miles east of Pittsburgh, during the shooting.

The 7.62 mm "minigun" is similar to ones used by the military on a wide variety of aircraft. It is rarely seen outside the military, said John Hageman, special agent for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

Kurty was an auxiliary police officer in Duncansville, and also worked with the county sheriff's department. He trained officers in many local police departments and "was proficient in all types of firearms," state police said.

At the demonstration, Kurty was working for East Coast Gun Sales, which owns the gun, authorities said. The company was offering a weapons exhibition and hosting a pistol shoot and dinner for those attending a three-day conference.

An employee at East Coast Gun Sales' store in Duncansville referred questions to state police.