Plea deal likely for 1 of 3 men charged in fatal homemade cannon incident

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NEW LONDON, Wis. (WSAW) -- One of three men investigators said constructed a cannon that exploded, resulting in a 44-year-old man’s death earlier this summer will reach a plea deal in the case.

Court records a plea and sentencing hearing has been scheduled on Oct. 23 for Kenneth Niemer, 43.

Investigators said on May 26 around 9 p.m. they responded to a home in the town of Dupont for a man injured when the 4-foot-long steel pipe exploded, striking the victim in the abdomen.

The victim recorded two videos of the incident, according to the complaint.

The two other suspects; Scott Mattes, 60; and Robert Mattes, 37 are expected to return to court Sept. 25 for clerical court appearance.

In the first video, court documents state Robert Mattes lit a fuse on a large pipe that was standing in a field. He then took off running. After a number of seconds there is a flash out of the top of the pipe. The video shuts off. In the second video, Robert Mattes again lights a fuse on the pipe and the fuse burns until it reaches the pipe. There is then a large explosion and the phone hits the ground.

According to Niemer, after the first attempt to light the explosive device failed, Scott Mattes put paper towels down the metal tube. He used a long wooden stick to pack the towels over the gunpowder. Scott Mattes then dropped an aerosol can of WD-40 down the pipe before Robert Mattes lit the fuse.

The victim, who has not been identified, died of a “penetrating fragment wound of abdomen” with a steel fragment removed during the autopsy, the complaint says.

All three are charged with homicide by negligent handling of explosives.