Third man sentenced for fatal explosion in Waupaca County

Waupaca County Jail photos

WAUPACA COUNTY, Wis. (WBAY) - A third and final suspect was sentenced for a fatal explosion in Waupaca County.

Shrapnel from a homemade cannon killed Paul A. Casperson of Belvidere, Ill., last May.

Monday, Robert Mattes, 38, of New London pleaded guilty to two charges: endangering safety with use of a dangerous weapon and disorderly conduct. The most serious charge, homicide by negligent handling of a dangerous weapon or explosive, was dismissed but read into the record.

Mattes was placed on probation for one year. He can avoid prison time if he follows the requirements.

Mattes' father, Scott D. Mattes, 60, of Marion, and Kenneth Niemer, 43, of Clintonville, were both given the same deal on the same charges last month: Their sentence was withheld if they follow the conditions of their probation for one year.

According o the criminal complaint, Niemer told investigators he brought what he called a "cannon" to a party at Scott Mattes' home in Marion. It was a pipe with a plug welded to the bottom.

Niemer said they put shotgun powder in the pipe, then the older Mattes added paper towels and dropped a can of WD-40 into it. Robert Mattes lit the fuse and they stood some distance away, then the metal contraption exploded.

District Attorney Veronica Isherwood called it a sad case at the men's bond hearing in May, acknowledging Casperson's death was unintentional. "Fireworks can be dangerous enough, and then when you make your own, it just is that much more dangerous," she said.