Before he was sentenced to five years in prison for possessing bomb-making materials, Brandon Russell, co-founder of a neo-Nazi paramilitary group, softly apologized to a federal judge for what he had done.

Yet five months later, the group Russell founded — Atomwaffen Division — posted a two-minute video starring Russell and threatening retaliation against "comrades ... who have abandoned ship."

It's not clear what, if any, role Russell played in the video, posted to the internet on May 23. It features a photo of Russell's face and a first-person narration.

And even if Russell did create or help create the video from behind bars, he is unlikely to face added punishment for it, legal authorities say. There were no conditions attached in January when the 22-year-old former Army National Guard private was sentenced in Tampa's U.S. District Court.

Still, those who study hate groups expressed concern about the video because a group they consider violent with links to as many as five slayings continues to go after new members, even after its leader was thrown in prison.

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"Extremist propaganda is often designed to recruit, reach and radicalize followers, and you never know who is going to respond and how," said Oren Segal, director of the Anti-Defamation League's Center on Extremism. "The combination of hate, glorification of violence and social media has proven time and again to have deadly consequences."

The video extols Adolf Hitler and the neo-Nazi cause and features images of uniformed men with semi-automatic rifles on maneuvers in the desert. It makes menacing references to former members.

"To all my loyal comrades who've stuck around, through thick and thin, I thank you for your ... courage and loyalty," the narrator says. "To all of those who have abandoned ship ... Adolf Hitler once said, 'There is no room in this world for cowardly people,' so there is certainly no room for you in the Atomwaffen Division."

"The sword has been drawn," the narrator says. "There is no turning back."

The register beneath the video recorded 4,710 page views as of Wednesday.

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First reported by Rolling Stone magazine, the 138-second video ends with images of three men described as former group members along with type listing their names and, in one case, community of residence.

Officials at the Atlanta federal prison where Russell is serving his sentence declined to comment. So did the U.S. Attorney's Office in Tampa.

The video and its content would only become a legal issue for Russell if he were subject to restrictions on his actions as a condition of release, said Tampa criminal defense attorney Patrick Courtney. The video may even be protected as free speech under the First Amendment, said Stetson University College of Law professor Charlie Rose.

Russell's involvement with Atomwaffen Division came to light as Tampa police investigated the May 19, 2017, shooting deaths of his roommates Andrew Oneschuk, 18, and Jeremy Himmelman, 22. A third roommate, Devon Arthurs, 19, is awaiting trial in the slayings. Investigators say Arthurs told them he fired the fatal shots to keep the other young men from committing domestic terrorism.

Russell was not charged in the deaths, but in searching his belongings, investigators found bomb-making materials as well as icons of white supremacy — Hitler's Mein Kampf, the apocalyptic novel The Turner Diaries and a framed photo of Timothy McVeigh, the former soldier and white supremacist executed for the 1995 Oklahoma City bombing.

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Atomwaffen Division is connected to five murders, including the two in Tampa, said Keegan Hankes, senior research analyst at the Southern Poverty Law Center's Intelligence Project. And the Naval Criminal Investigative Service is looking into allegations that another group member, Marine Lance Cpl. Vasillios Pistolis, took part in a violent attack during an August 2017 white-supremacist rally in Charlottesville, Va.

Given the group's history of violence, Hankes said the three former Atomwaffen group members mentioned in the Russell video could be in danger.

"These groups are organized as decentralized terror cells," Hankes said. "It would be my assessment of the group, given what we know about their ideology and what they have already done, that they are a danger."

But even if something did happen to the men, proving Russell's complicity would be a challenge, attorney Courtney said.

If it were proven he helped make the video, the next step would be proving he knew it to be a call to harm another individual and therefore a "conspiratorial act," he said.

"The problem," Courtney said, "lies in the proof of all those elements if something were to happen."

Contact Howard Altman at haltman@tampabay.com or (813) 225-3112. Follow @haltman