But others, including the boy's father, made the fatal decisions, a defense attorney said.
Former Pelham Police Chief Edward Fleury, whose company co-sponsored the event, has pleaded not guilty to involuntary manslaughter and furnishing a weapon to a minor in connection with the 2008 death of Christopher Bizilj of Ashford, Conn.
"As a direct result of that reckless and illegal behavior, Christopher died," District Attorney William Bennett said in his opening statement to the jury in Hampden Superior Court.
Bennett said Fleury's advertising for the event falsely said there was no age limit or license required to shoot machine guns.
"Fleury represented that it was all legal and fun," Bennett said. "The evidence will show that one of the purposes of Fleury's enterprise was to furnish machine guns to children."
Bennett said the boy's father, Dr. Charles Bizilj, "thought this would be a great adventure and a lot of fun for the boys."
Bizilj brought his two sons, 11-year-old Colin and 8-year-old Christopher, to the event. Colin fired the Uzi first with no problem.
Then Christopher went to fire the gun. Bennett said an unlicensed and uncertified 15-year-old boy was helping Christopher.
The teenager gave the Uzi to Christopher and had one hand on the boy and one on the gun, Bennett said.
"It was illegal to allow that child to have the weapon in the first place," Bennett told the jury. "Christopher is not capable of controlling this weapon. You will learn that this weapon fires 1,200 rounds per minute.
"He (Christopher) puts his finger on that trigger. It flips back. The small size of the gun makes it possible for the muzzle to come right back into his face," the prosecutor said.
Bennett said a bullet went through Christopher's face.
A retired state medical examiner, Dr. Loren Mednick, testified Tuesday that Christopher suffered such extensive brain damage and bleeding that it was impossible to save him.
A graphic video of the accident recorded by the boy's father is expected to be introduced as evidence. Judge Peter Velis ruled Monday over the objections of prosecution and defense attorneys that there is no legal reason to prohibit media access to the video.
Defense lawyer Rosemarie Scapicchio said the event was controlled and organized. She said Fleury got town permission and that others on the firing line had final say over who could shoot the guns, and Fleury wasn't one of those people.
She said two other people also charged in the case brought the machine guns to the exhibition.
Scapicchio said Charles Bizilj decided to bring his sons to the machine gun shoot, signed their names to the liability waiver form and picked out the Uzi.
"He made the decision as a parent that this was safe for his children to do," Scapicchio said. "But as a parent, as a parent, you have to take some responsibility. Chief Fleury did nothing wrong."
Scapicchio also said state law at the time allowed minors to temporarily hold machine guns, as long as they were with a licensed person and on a firing range.
"This whole idea that Chief Fleury was reckless ... is simply untrue," Scapicchio said.
The two men who supplied the guns, Carl Giuffre and Domenico Spano, both of Connecticut, had conducted the same gun shoot at the Westfield club for seven years without incident. Giuffre and Spano have pleaded not guilty to involuntary manslaughter and are awaiting trial.
Charles Bizilj was not charged because he was a layman and based his decision to allow his sons to fire the gun on information from others who should have known it was too dangerous, prosecutors have said.