A small-town Massachusetts police chief who authorities say promoted, organized and profited from a firearms exposition where children were encouraged to shoot machine guns and where an 8-year-old killed himself with a Micro Uzi was charged Thursday with involuntary manslaughter.

Although the event was promoted as an opportunity for children to fire machine guns under the supervision of certified instructors, 8-year-old Christopher Bizilj had been supervised by a 15-year-old boy who was “knowledgeable about guns” but not certified as a firearms instructor, Hampden County District Attorney William M. Bennett said in outlining charges against Pelham Police Chief Edward B. Fleury and two others.

The Oct. 26 death at the Machine Gun Shoot and Firearms Expo at the Westfield Sportsman’s Club horrified the region and provoked outcry from parents, lawmakers and some gun enthusiasts who condemned it as a senseless tragedy.

In the event, the 8-year-old’s father, Dr. Charles Bizilj, stood 10-feet behind his son while the boy aimed at a pumpkin with an automatic weapon that fires 1,700 rounds a minute and is notoriously difficult to handle. When Christopher squeezed the trigger, the gun jerked out of control and fired a bullet into the right side of his head.

Thursday’s indictment was authorities’ attempt to assess responsibility for the death.

Bennett said the boy’s father had taken Christopher to the gun show and chose the Micro Uzi for him to fire but would not be charged. “He is already being punished and will continue to be punished” in mourning Christopher’s death for the rest of his life, Bennett said.

Fleury, Pelham’s police chief of 22 years, was singled out as the central force behind the expo. He organized it through a business he ran, COP Firearms & Training, and marketed it in advertisements that said the $5 entry fee was waived for children under age 16 and that there was “no age limit or licenses required to shoot machine guns.”

Bennett said Fleury took a portion of the proceeds from the event. He was charged with involuntary manslaughter, which carries a penalty of up to 20 years in prison.