Clad in a black Punisher mask and body armor, the young man provoked concern among those at a Prior Lake firing range this fall as he ran through rapid drills that expelled hundreds of rounds of ammunition in short order.
Within weeks, FBI agents and informants listened as River William Smith idolized as a "hero" the mass shooter behind the attack on a Colorado Springs LGBTQ club. They recorded him discussing his interest in joining neo-Nazi paramilitary groups. And they helped piece together plans that he believed would add explosives and automatic weapons to an arsenal he intended to use against police.

Agents on Wednesday arrested the 20-year-old Savage man as he handed over cash to one of the informants in exchange for grenades and auto sear devices that would render firearms fully automatic.
The investigation — which yielded federal criminal charges of illegally possessing a machine gun and attempting to receive and possess destructive devices — saw agents tail Smith to the firing range and informants record his increasingly apocalyptic views about police and minorities.
"Most cops can't shoot. You'd be surprised," Smith allegedly told one of the informants in the case during a text exchange. "We're all going to die. It's not up to me to decide when. So I take it as whenever god says I'm done they'll turn up. And I can put all the training to use. I'm not looking for a big gunfight. But I hated life without guns."
Smith was referring to a 2019 incident when he was 17. At the home he shared with his grandparents in Savage, he fired three rounds from an AK-47-style assault rifle — one of which struck his grandmother in the hand. Police later seized that rifle, two loaded handguns, one .22 caliber rifle and a shotgun from Smith. Police also recovered 15 fully loaded 7.62mm magazines, tactical equipment, full ammunition cans and pistol magazines. At the time, law enforcement also turned up web searches about Hitler and Nazis, videos of gay people being killed and bombmaking instructions.
Smith attracted the attention of the FBI's Joint Terrorism Task Force this year when a concerned citizen — himself a former police officer who worked at the gun range Smith frequented — called the bureau's National Threat Operations Center in September to report troubling behavior at the range. The same caller already knew of Smith from his past service as a police officer around the time of the 2019 shooting incident.
An attorney for Smith could not be identified on Thursday. Messages were left for relatives of Smith.