PHOENIX — The accidental shooting death of a firing-range instructor by a 9-year-old girl with an Uzi has set off a powerful debate over youngsters and guns, with many people wondering what sort of parents would let a child handle a submachine gun.

Instructor Charles Vacca, 39, was standing next to the girl Monday at the Last Stop range in White Hills, Arizona, about 60 miles south of Las Vegas, when she squeezed the trigger. The recoil wrenched the Uzi upward, and Vacca was shot in the head.

Prosecutors say they will not file charges in the case.

Gerry Hills, founder of Arizonans for Gun Safety, a group seeking to reduce gun violence, said that it was reckless to let the girl handle such a powerful weapon and that tighter regulations regarding children and guns are needed.

“We have better safety standards for who gets to ride a roller coaster at an amusement park,” Hills said. Referring to the girl’s parents, Hills said, “I just don’t see any reason in the world why you would allow a 9-year-old to put her hands on an Uzi.”