The slayings of two young men in Florida, allegedly at the hands of their roommate, has exposed disturbing evidence of a credible neo-Nazi threat to public safety, federal investigators say.

Devon Arthurs, the 19-year-old co-founder of the obscure neo-Nazi group "Atomwaffen Division," was arrested in the May 19 fatal shooting of his roommates, 18-year-old Andrew Oneschuk and 22-year-old Jeremy Himmelman.

At the time of the arrest, officials said Arthurs claimed he killed Oneschuk and Himmelman to thwart a domestic terrorist attack by Atomwaffen, which is German for “atomic weapon.”

“I prevented the deaths of a lot of people,” Arthurs said in a rambling statement, according to officials. Asked why his roommates planned such an attack, he said, “Because they want to build a Fourth Reich.”

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This undated photo provided by Kianna Kaizer, shows Jeremy Himmelman and his girlfriend Kianna Kaizer. (Kianna Kaizer via AP)

Atomwaffen doesn’t have near the numbers or notoriety of some of the white nationalist and neo-Nazi groups that gathered in Charlottesville, Va., for a rally that led to deadly clashes earlier this month.

William Tschantre, 20, another member of Atomwaffen, denied the group was planning any attacks, saying the members were simply a band of so-called trolls who delight in provoking outrage with stunts.

“I’m a neo-Nazi. I am not a monster,” he told the Associated Press. “We’re not here to, like, bomb the U.S. government. That’s absolutely ridiculous.”

The scene depicted inside the young men’s residence, however, paints a different picture, authorities say.

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Brandon Russell is facing charges related to explosives that were found. (AP)

Inside the Tampa apartment – which Arthurs, Oneschuk and Himmelman shared with 21-year-old Brandon Russell – police found guns, ammunition and bomb-making material, along with a framed photo of Oklahoma City bomber Timothy McVeigh.

In the condo’s garage, bomb squad technicians found volatile explosive material stored in a cooler, near homemade detonator components and several pounds of ammonium nitrate. Two sources of radiation were also detected on the premises, authorities said.

Arthurs claims Russell knew nothing of the killings, but accused him of stockpiling explosives to bomb power lines, nuclear reactors and synagogues.

In anonymous internet posts, Atomwaffen members hailed Oneschuk and Himmelman as fallen heroes and assailed Arthurs as a race traitor.

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This April 2017 photo provided by his family shows Andrew Oneschuk during his 18th birthday party, (Christin Oneschuk via AP)

Relatives and friends of the two slain men reject any neo-Nazi labels, but do not dispute they held far right-wing ideologies. They say the two men were moving on to new phases in their lives.

“Jeremy went through a lot of struggle in his life, and national socialism offered him the rigidity he desired, and offered him solutions for things out of his control,” Kianna Kaizer, Himmelman’s girlfriend said in an email. “So it’s been really hard to try and tell his family, but yes he did hold white supremacist beliefs and national socialist beliefs.”

According to relatives, the four young men met online last year, and the lure of a rent-free home and the prospect of bountiful fishing convinced Himmelman and Oneshuck to move from Massachusetts to Florida for the summer.

Himmelman was in a financial rut and open to a fresh start when Russell began pressuring him to move to Tampa, friends and family said. He had toyed with joining the military, they said, but instead planned to use his Florida experience to figure out his next move.

And Andrew Oneschuk's father said his son had met with a Navy recruiter in April, on his 18th birthday, and looked forward to starting a military career.

Once the pair arrived in Florida, tensions between the roommates quickly mounted. Kaizer said Himmelman and Oneschuk often teased Arthurs for having no job and spending most of his time playing video games.

"Jeremy went down there expecting a break from the stress he was under in Massachusetts," she said. "As soon as Jeremy arrived in Florida, the stark difference between the promises made and reality were apparent."

According to Tschantre, Arthurs recent conversion to Islam and his religious rhetoric also annoyed other Atomwaffen members. He said the night before the shooting, Arthurs got into an argument with other members online, which Tschantre said he suspects could have played a part in triggering Arthurs' anger into violence the next evening.

Earlier this month, prosecutors said they would not seek the death penalty against Arthurs, who faces two counts of first-degree murder. Russell, who was not involved in the killings, is facing charges related to the explosives recovered.

Russell has denied any plans to make a bomb, saying the materials were used to boost model rockets.

The Associated Press contributed to this report.