TAMPA — Brandon Russell had bombmaking materials in his apartment because he wanted to "kill civilians and target locations like power lines, nuclear reactors, and synagogues," according to a federal court document filed by prosecutors late Monday.

That assertion is based on law enforcement interviews with Devon Arthurs, one of Russell's three roommates who is accused of killing the other two at their Tampa Palms apartment.

Prosecutors are using his account to again ask a federal magistrate judge to deny bail for Russell, a Florida National Guardsman who was charged with having bombmaking materials in the wake of the killings.

U.S. Magistrate Judge Thomas B. McCoun has ruled that Russell is entitled to post bail while he awaits trial, though he hasn't set an amount. Prosecutors say Arthurs' account shows Russell poses an extreme danger to the community and are asking the judge to revoke his earlier ruling. A hearing on the matter is scheduled for 11:30 a.m. today.

The newly filed written arguments offer alarming new details of the investigation that began May 19 after Arthurs led authorities to the bodies of the two other roommates.

Arthurs remains jailed on state murder charges in the deaths of Andrew Oneschuk and Jeremy Himmelman. Police said he admitted killing the two because they were neo-Nazis who had disrespected his conversion to Islam.

When he led officers to their bodies, they encountered Russell outside, visibly upset.

Arthurs told police that Russell knew nothing about the murders, according to the federal court document. He also told them about Russell's leadership of the Atomwaffen neo-Nazi group.

The same night, Russell spoke with investigators and admitted that the various bomb-making materials they found in an adjacent garage belonged to him, the document states. He told them he wanted to see his father in West Palm Beach and left.

The next day, Russell was charged with possession of an unregistered destructive device and unlawful storage of explosive material. Contacted by law enforcement, his family said they had not heard from him and did not know where he was.

Monroe County sheriff's deputies found Russell in a Burger King restaurant in Key Largo. With him was another man, identified in a Monroe County sheriff's report as William James Tschantre, 20. Reached via phone Monday, Tschantre declined to talk to a reporter.

The U.S. Attorney's court document does not identify the man who was with Russell.

In Russell's car, investigators found two long guns and more than 500 rounds of ammunition, prosecutors said. They had purchased the items at a Bass Pro Shops store in Homestead.

The other man, according to prosecutors, described himself as one of Russell's best friends. They had met in an online forum dedicated to discussions of fascism, Nazism and "current trends" in hate for the government, according to the prosecutors' motion.

He said he had visited gun shops and ranges with Russell, the document states. He knew Arthurs, Himmelman and Oneschuk and had planned to move in with them before the murders.

He said the Atomwaffen group had about 30 members nationwide, according to the court document. And he said Russell screened those who wanted to join because he did not want those who were "complete idiots."

Russell's friend had quit his fast-food job and grabbed his life savings of $3,000 before leaving town with Russell. He said they had no specific destination and no plans to harm anyone.

Russell, questioned a second time, admitted again that the explosives were his, prosecutors said, but claimed they were for "amateur rockets." When asked about the Atomwaffen group, he ended the interview.

Times staff writer Howard Altman contributed to this report. Contact Dan Sullivan at dsullivan@tampabay.com or (813) 226-3386. Follow @TimesDan.