WESTFIELD, Mass. (AP) — 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 Valliere said.

The boy, Christopher Bizilj of Ashford, Conn., was with a certified instructor and “was shooting the weapon down range when the force of the weapon made it travel up and back toward his head, where he suffered the injury,” a police statement said.

Christopher died at Baystate Medical Center.

Although police called it a “self-inflicted accidental shooting,” police and the Hampden district attorney’s office were investigating, officials said.

“We are going to review all the circumstance regarding what happened, who was involved, what authorities they may or may not have had, who was supervising,” District Attorney William Bennett said Monday.

It is legal 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.

Those conditions were met in this case, he said. He declined to release the supervisor’s name.

The club said on its Web site that the event, run in conjunction with C.O.P Firearms and Training, is “all legal and fun.” People are allowed to fire weapons at vehicles, pumpkins and other targets, it said.

Officials of the private club and the firearms group could not be reached for comment. There was no response to a message left on a club answering machine. The C.O.P. group’s machine clicked off without taking a message.

The sportsman’s club was founded in 1949 and describes itself on its Web site as promoting “the interest of legal sport with rod, gun, and bow and arrow, both directly and through training.”