This Dec 15, 2022 booking photo released by Sherburne County Jail in Elk River, Minn., shows River Smith. The Minnesota man who authorities say had idolized the man who killed five people at a gay nightclub in Colorado Springs and was building an arsenal to use against police was arrested this week as he allegedly tried to buy grenades from an informant. (Sherburne County Jail via AP)

SAVAGE, Minn. (AP) — A Minnesota man who idolized the shooter who killed five people at a gay nightclub in Colorado Springs and was allegedly building an arsenal of automatic weapons to use against police was arrested this week after a retired police officer reported his behavior to authorities, according to federal charges.

The warning signs -- strikingly similar to the circumstances that preceded the shooting at Colorado's Club Q last month -- prompted a monthslong federal investigation into River William Smith, and resulted in a far different outcome.

Smith, who also expressed interest in joining neo-Nazi paramilitary groups and fired an AK-47-style rifle in his home in 2019, was charged with federal weapons counts this week. FBI agents arrested the 20-year-old man Wednesday after he purchased three hand grenades and four auto sears from an FBI informant, according to the U.S. Attorney's Office. An auto sear is a device that turns a firearm into an automatic weapon.

Smith, who lives in the Minneapolis suburb of Savage, had told the informant that the shooter who killed five people at an LGBTQ nightclub last month was a “hero,” called Black people “agents of satan,” and said he was ready to engage the police “with armor and full autos," according to an FBI affidavit.

Smith remained in custody Friday and is scheduled to appear in court Tuesday. Online court records show he is being represented by the Office of the Federal Defender. Phone and email messages seeking comment on his behalf were not immediately returned Friday.

The timely FBI investigation and arrest provided a sharp contrast to the warning signs that were ignored and earlier charges that were dismissed against Anderson Lee Aldrich, who was charged with hate crimes in the mass shooting at a Colorado gay nightclub, said George Washington University Law Professor Jonathan Turley.

“The only way to protect the public is to move expeditiously and aggressively,” he said of potentially violent people like Smith. “That was a missing element in the earlier case. In many ways, it’s a cautionary tale for law enforcement: These early signals cannot be missed."

In both cases, the suspects’ grandparents had been previously injured in run-ins with them but had later appeared to enable their alarming behavior.

In Smith’s case, authorities say his grandmother drove him to the shooting range where he was seen practicing shooting drills, firing off hundreds of rounds in just a few minutes. Relatives of Aldrich’s grandparents have said they gave Aldrich about $30,000 to buy a 3-D printer that they said he used to make gun parts.

A Colorado SWAT team in 2019 uncovered a stockpile of more than 100 pounds (45 kilograms) of explosive material, firearms and ammunition in Aldrich's home. Aldrich was charged after the standoff, but the case unraveled. Authorities say that less than two years later, on Nov. 19, Aldrich fatally shot five people.

In Smith's case, he was 17 when he fired an AK-47-style rifle in the house where he lived with his grandparents in 2019, according to court documents. His grandmother, who received a minor injury to her hand, told officers at the time that she had taken two pistols from Smith and hidden them in her closet. The grandparents told police they were concerned for their safety if Smith was released from custody.

The grandmother, Roberta McCue, told The Associated Press on Friday that she didn’t want to comment because she was “exhausted,” but added that her hand was injured in 2019 when she cut it on a doorknob.

According to court documents, she told police in 2019 that Smith acted “possessed” that night, and she described him as “big and scary and strong.” She also said Smith's mother, who was living in Wisconsin, had purchased the firearm in her name and given it to Smith. His grandfather had also given him a shotgun to go skeet shooting, the documents show.

During follow-up searches, police found tactical equipment, 15 fully loaded magazines, full ammunition cans and a go-bag of water and canned goods that suggested to them he could have been preparing for a prolonged standoff. The FBI affidavit also says Smith’s electronic devices revealed Internet searches about Adolf Hitler and videos of gay people being killed. An external hard drive contained files about building bombs.

As part of a probation agreement, Smith was barred from using or possessing any firearms until he turned 19. Less than two years later, he was stockpiling firearms and enough ammunition to fire a fully automatic weapon, authorities said.

Minnesota does not have a red flag law, which allows judges to temporarily take weapons away from people determined to be a threat to themselves or others. State law prohibits anyone under the age of 18 from purchasing a firearm or ammunition. However, it does allow for minors to possess ammunition and semiautomatic weapons or handguns when in the presence or supervision of a guardian.

State Rep. Dave Pinto, a Democrat who also works as a prosecutor, said, “There is a lot more we could be doing to keep guns out of the hands of people who have shown themselves to be dangerous."

Democrats have pushed for a red flag law in the state in recent years, and are planning to again next year.

Smith came to the attention of the FBI this fall, after he frequented a firearm range and gun club wearing tactical gear, body armor and a “Punisher” mask, which the FBI said has been used by right-wing extremist groups to reference “the last thing a victim sees.”

A retired police officer who worked at the gun range contacted the FBI’s National Threat Operations Center on Sept. 27 after he saw Smith shooting from behind a plywood barricade he had assembled and practicing rapid reloads of his handgun, according to the affidavit.

The operations of a different gun shop said Smith had been banned from buying weapons there after his 2019 arrest. Billy Luetkahans, operations manager of the Modern Sportsman gun shop and shooting range in Burnsville, said the store also banned others from buying guns for Smith. Still, he said, Smith had visited the store within the past year to look around.

If the store had known about Smith’s interest in neo-Nazism, “that would’ve been brought up and we’d have banned him completely from the property,” Luetkahans said. “Any sort of hate like that, we just don’t tolerate.”

According to the FBI affidavit, Smith told an informant that he was “pro mass shooting in general,” and that he wanted to add the hand grenades to his tactical vest. He said it was part of a personal arsenal that included a note cursing police officers stowed in his tactical gear.

“They can find that once they get me,” he allegedly told the informant in a recorded conversation. “When they're scooping their boys up.”

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This story has been edited to correct the attribution to The U.S. Attorney's Office.

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Groves reported from Sioux Falls, South Dakota. Associated Press writer Amy Forliti in Minneapolis contributed to this report.

News from © The Associated Press, 2022