(CNN) -- A Minnesota man who federal authorities say expressed admiration for mass shooters was arrested Wednesday after allegedly trying to purchase hand grenades and a firearm component that converts an AR-15 style rifle into an illegal machine gun, the Justice Department announced.
River Smith, 20, has been charged with one count each of illegal possession of a machine gun and attempting to receive and possess destructive devices, according to a criminal complaint.
During an FBI investigation, Smith told a government informant that he is "pro mass shooting." He also expressed sympathy for the Parkland school shooter and called the person charged in the recent shooting at a Colorado Springs LGBTQ nightclub "a hero," according to the complaint.
"Smith stated that he was preparing to fight the police and was dedicated to dying in that fight," the Justice Department said.
On Wednesday, Smith was arrested after he allegedly purchased three hand grenades and four illegal machine gun conversion parts from the government informant, the press release said. He was wearing soft armor and carrying a loaded handgun at the time of his arrest, the complaint said.
CNN has reached out to Smith's attorney.
Smith was reported to the FBI in September by a retired police officer who works at a gun range Smith frequented, according to the complaint. The retired officer said he saw Smith -- dressed in plated armor designed to stop bullets -- performing rapid reload drills and shooting hundreds of rounds of ammunition in a short period of time, the complaint says.
Over the course of the investigation, Smith told a confidential government source that he has an "intense dislike" of minorities, Jewish people and gay people and expressed racism toward Black people, according to the complaint.
He also told another government source that he was previously interested in joining a neo-Nazi group, the complaint says.
Smith made his initial appearance in U.S. District Court Thursday and will remain in custody pending further proceedings, according to the release.
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