SPEARFISH, S.D. – A Spearfish man has been sentenced to five years and 11 months in prison after being convicted on two counts of possession of an unregistered firearm.

Cole Nygaard pleaded guilty to the charges in July of 2026.

Prosecutors say in January of 2024, in Lawrence County, Nygaard was the passenger in a vehicle that was stopped by law enforcement. Officers were looking for the driver after receiving reports that he intended to kill someone. Inside the car were three firearms with silencers affixed to the end of the barrels. The silencers were devoid of any markings or serial numbers and were not registered in the National Firearms Registration and Transfer Record (“NFRTR”) as required by law.

Nygaard’s possession of the unregistered silencers was a violation of federal law.

On January 27, 2026, law enforcement conducted a search of Nygaard’s residence after learning he was making pipe bombs and indicated he would use them on others and a business. Inside the house, law enforcement officers discovered nine improvised explosive devices (IEDs) that Nygaard manufactured, including metal pipe bombs and a victim-operated metal box that could be readily assembled into a destructive device.

Authorities say one of the smaller IEDs detonated when law enforcement officers attempted to render the device safe. Fortunately, due to precautionary measures taken by them, no one was injured because of the explosion.

Nygaard was also ordered to serve three years of supervised released upon completion of his sentence.