Utah cops are trying to determine what triggered a tiny replica cannon to fire something into the face of a 14-year-old boy, killing him. "We're waiting for the autopsy," said Joyce Hansen, administrative assistant to the chief of police in Tremonton, Utah. She said it might take weeks, depending on the workload of the state medical examiner's office in Salt Lake City. Robby Ostberg died Monday when the replicate 18th century cannon he was holding fired accidentally, a police press release said. According to the release, Ostberg had been playing video games with his 16-year-old brother when the cannon erupted. He was dead when police arrived, the release said. The release said the cannon was a .50-caliber weapon designed to be fired with black powder. Police did not know what type of propellant may have been in the cannon Monday or if there had been a projectile in it, police said. Robby Ostberg often filled the cannon with black powder and fired tinfoil balls out of it, Cameron Kunsman, who called Robby his best friend, told the Deseret News. Trever Steinlicht, a neighbor, said cannons like the Ostbergs' could send a projectile through a wall or kill "small game," ABC4 said. They are known to go off accidentally, he said. "All it takes is for something to slip and the hammer to drop on it and it will go boom," Steinlicht said. There is legal confusion over whether the miniature cannons are decorations, toys or firearms, according to a blog post by legal scholar Jonathan Turley. "Utah laws are silent on replica firearms and antique firearms," he notes. If the cannon that killed Ostberg was designed to fire a .50-caliber round, Turley asks, should it be treated as a firearm and should it come with warnings and a safety lock, he asks. Ostberg's father, Allen Ostberg, was home at the time of the accident, the release said. A relative told ABC4 Salt Lake City that Ostberg was an Army veteran who had guns in the home, but he locked them and taught his sons gun safety.