Authorities say a hidden camera captured members of a violent white supremacist group expressing hope that violence at a gun rights rally in Virginia this week could start a civil war.
A federal prosecutor disclosed the existence of the video in a court filing Tuesday.
The prosecutor said former Canadian Armed Forces reservist Patrik Jordan Mathews also videotaped himself advocating for killing people, poisoning water supplies and derailing trains.
Assistant U.S. Attorney Thomas Windom is urging a judge in Maryland to keep Mathews and two other members of The Base detained in federal custody.
FBI agents on Thursday arrested Mathews and two other men who are linked to violent white supremacist group The Base.
Mathews, 27, and Brian Mark Lemley Jr., 33, of Elkton, Maryland, are charged with transporting a firearm and ammunition with intent to commit a felony. William Garfield Bilbrough IV, 19, of Denton, Maryland, is charged with transporting and harboring aliens.
The three men were believed to be planning to attend the pro-gun rally Monday in Richmond, according to a law enforcement official who spoke to The Associated Press on condition of anonymity to discuss an active investigation.
Mathews and Lemley were arrested in Delaware, and Bilbrough was arrested in Maryland, according to Marcia Murphy, a spokeswoman for the U.S. Attorney's office in Maryland.
Court papers say Mathews illegally crossed the U.S. border near Minnesota in August and investigators allege Lemley and Bilbrough then drove from Maryland to Michigan to pick up Mathews before the three headed to Maryland in late August.
U.S. and Canadian authorities had been searching for Mathews after his truck was found in September near the border between the two countries. He was last seen by family members in Beausejour, northeast of Winnipeg, on Aug. 24, according to the Royal Canadian Mounted Police. The Canadian military's intelligence unit was investigating Mathews for "possible racist extremist activities" for several months, according to the Canadian Department of National Defence.
Authorities say Lemley and Mathews built an assault rifle using several parts, including an upper-receiver that Lemley had ordered and shipped to a Maryland home. In December, the three men gathered at an apartment that Lemley and Mathews rented in Delaware, where they discussed The Base and its activities and members, passed around the assault file and tried to make the drug DMT, a hallucinogen, according to court papers.
A few days later, Lemley and Mathews bought 150 rounds of ammunition and paper shooting targets and Lemley was spotted by an FBI agent at a gun range in Maryland. Court papers say federal agents heard the gun firing in rapid succession and authorities allege that Lemley later told Mathews: "Oh oops, it looks like I accidentally made a machine gun."
Federal agents appeared to be tracking the men's movements and set up a stationary camera near the gun range, which captured video of Mathews shooting the gun there on Jan. 5. Court documents say Lemley had also ordered 1,500 rounds of ammunition and he and Mathews visited the gun range as recently as Saturday.
Lemley also is charged with transporting a machine gun and "disposing of a firearm and ammunition to an alien unlawfully present in the United States."
The Anti-Defamation League said members of The Base and other white supremacist groups have frequently posted online messages advocating for "accelerationism," a fringe philosophy in which far-right extremists "have assigned to their desire to hasten the collapse of society as we know it."
"The term is widely used by those on the fringes of the movement, who employ it openly and enthusiastically on mainstream platforms, as well as in the shadows of private, encrypted chat rooms," the ADL says.