EDMONTON (CBC) - A central Alberta man has been charged in the death of a teen who was killed when a pen-like device used to scare off bears went off in a truck and struck him with a bullet.

Tanner Mayer, 15, and his friend were sitting in the parked truck outside a home in Rocky Mountain House on Sept. 7 when the friend found the device on the floor of the vehicle.

The device discharged and a bullet struck Mayer at close range. He died later in hospital.

"The autopsy revealed that what was discharged from that was a .22-calibre bullet," said RCMP Sgt. Chris Matechuk.

The device, known as a bear banger, is commonly used to fire a signal flare and create a loud bang to scare off bears, but it was somehow modified to carry a bullet.

The friend's father, James Alexander Rose, 41, has been charged with criminal negligence causing death, manufacture of a prohibited device, and careless use of a prohibited device, RCMP said Friday.

Mayer's death was hard on his high school friends and the town of about 7,000 people, about 200 kilometres northwest of Calgary.

"Tanner and the friend were close friends, known by everybody in the community," said Matechuk.