MINNEAPOLIS (WCCO) — A threat to blow up the homes and vehicles of a judge and a prosecutor in Kandioyhi County has led investigators to a stash of weapons.

A search of Chad Monson’s house and property uncovered rifles, handguns, machine guns, ammunition, bomb-making materials and drugs.

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Monson and four others living in the home were arrested, and have all spent the last month behind bars inside the Kandiyohi County Jail.

Sheriff Dan Hartog said it is one of the most unusual and concerning cases he has seen in Willmar.

Chad Monson (credit: CBS)

“Why are they stockpiling something like that? And, yeah, what were you going to do with this stuff?” Hartog said.

Court papers show Monson told someone he had a plan. He had located where a judge, a prosecutor and another attorney lived and planned to use — or “plant” —
explosives near their vehicles or homes.

Investigators searched Monson’s home and found an arsenal of weapons, including machine guns, 10,000 rounds of ammunition and a grenade launcher.

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“The thing to us was the amount of fully-automatic weapons that were found,” Hartog said. “That’s a concern, because they have a fully-automatic weapon, you have to have a special permit. And then along with that were the pipe bombs.”

Monson’s excavating business — one of the locations where weapons, explosives and drugs were found. (credit: CBS)

On Feb. 21, three weeks after his arrest, a second search warrant was executed here at the site of Monson’s excavating business. They found more illegal weapons, more explosives and drugs in a shed.

The list of what was found includes pipe bombs with intact fuses, pails with explosive materials and more machine guns.

The Minneapolis Bomb Squad was called in to detonate the explosives.

“They didn’t know how stable [the bombs] would be, so they just detonated it right there,” Hartog said.

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A judge set Monson’s bail at $500,000. Investigators are still looking into where he purchased all those illegal weapons and explosives.