Suspect Charged In Fatal Homemade 'Cannon' Explosion Pleads Not Guilty

WAUPACA, Wis. (CBS Local) -- One of three Wisconsin men charged with making a homemade "cannon" that exploded, killing a man, pleaded not guilty, authorities said.

42-year-old Kenneth Niemer of Clintonville, 37-year-old Robert Mattes of New London and 60-year-old Scott Mattes of Marion are charged with homicide by negligent handling of explosives, a felony.

Niemer waived a preliminary hearing June 11, and entered a not guilty plea, WLUK reported. No trial date has been scheduled, according to court records.

The men were using a 4-foot-long, half-inch-thick steel pipe with a plug welded onto the bottom, according to the criminal complaint. The device exploded at a home in Marion, sending a piece of shrapnel that killed Paul Casperson, 44, of Belvidere, Illinois, on the evening of May 26.

"They were having a reunion party and they decided to entertain themselves by setting off explosives," said Waupaca County District Attorney Veronica Isherwood. "These are all people that have no criminal record and they all have strong ties to the community and we don't believe there was anything intentional about this."

"Niemer indicated he had brought a pipe, that he had manipulated with a plug welded onto the bottom, over to the party. He described the device as a 'cannon.' He indicated 'we dumped shotgun powder in the tube. We lit it once and it just flared up. We did it again but this time we used some paper toweling and put it in the pipe with a stick. We all stood by the fence. [The victim] was standing by the side of the camper. When it went off, he landed on the ground,'" the complaint states.

Casperson died of a "penetrating fragment wound of abdomen" with a steel fragment removed during the autopsy, the complaint says.

The men face up to 10 years in prison, if convicted.