An 8-year-old boy died after accidentally shooting himself in the head while firing an Uzi submachine gun under adult supervision at a gun fair.

The boy lost control of the weapon while firing it Sunday at the Machine Gun Shoot and Firearms Expo at the Westfield Sportsman’s Club, police Lt. Lawrence Vallierpratte said.

Police said the boy, Christopher Bizilj of Ashford, Conn., was with a certified instructor and called the death a “self-inflicted accidental shooting.”

As the boy fired the Uzi, "the front end of the weapon went up with the backfire and he ended up receiving a round in his head," police Lt. Hipolito Nunez said. The boy died at a hospital.

The boy's father and older brother were also there at the time, a gun club member and school official said. Francis Mitchell, a longtime member and trustee of the club, said he was told the boy's father was supporting his son from behind when the shooting happened.

Although the death appeared to be an accident, officials were investigating.

It is legal in Massachusetts for children to fire a weapon if they have permission from a parent or legal guardian and are supervised by a properly certified and licensed instructor, Lt. Hipolito Nunez said. The name of the instructor helping the boy was not released.

The event ran in conjunction with C.O.P Firearms and Training, said in an ad that people are allowed to fire weapons at vehicles, pumpkins and other targets at the event.

"It's all legal & fun — No permits or licenses required!!!!" reads the ad, posted on the club's Web site.

Messages left on answering machines for the club and the C.O.P. group were not returned Monday.