Outside the apartment, a fourth roommate, 21-year-old Brandon Russell, was "crying and was visibly upset," police said.
"He doesn't know what's going on and just found (the two dead roommates) like you guys did," Arthurs told police.
What followed was a chilling confession in which Arthurs described in "specific details" how and why he had killed two of his roommates earlier, police said. According to records, Arthurs told officers that "all of them had been friends with a common neo-Nazi belief" until Arthurs converted to Islam:
Since then, Arthurs stated, he has become angered by the world's anti-Muslim sentiment and had wanted to bring attention to his cause. Arthurs also stated that, before the murder, he had been privy to neo-Nazi Internet chat sites threatening to kill people, and he had developed a thinking that he should take some of the neo-Nazis with him.
Arthurs had displayed some of his ideology when he walked into the Green Planet Smoke Shop - presumably after killing his roommates - and produced a gun, ordering a customer and employee to "get the (expletive) on the ground," according to police.
After a second customer walked into the store, Arthurs told all three hostages that he had already killed someone and was "upset due to America bombing his Muslim countries," a police report stated.
When Tampa police officers arrived about five minutes later, Arthurs surrendered after a brief standoff and was placed under arrest. According to police, he exclaimed "Allah Mohammed!" as he was being walked to a patrol car, and told officers: "I had to do it. This wouldn't have had to happen if your country didn't bomb my country."
County arrest records indicate Arthurs was born in Florida.
In a search of the apartment Arthurs shared with his three roommates, officers discovered bomb-making equipment in the garage, including fuses and a cooler containing a "white cake-like substance" that bomb squad technicians recognised as the explosive HMTD (hexamethylene triperoxide diamine), according to a criminal complaint filed by the FBI in US District Court.
Inside a bedroom belonging to Russell, the roommate who had been crying when police arrived, officers found firearms, ammunition and "Nazi/white supremacist propaganda," including a framed picture of Oklahoma City bomber Timothy McVeigh on the dresser. McVeigh was sentenced to death for the 1995 bombing of the Alfred P. Murrah Federal Building, which killed 168 and was the deadliest terrorist attack on American soil before September 11, 2001.
Russell told investigators that he had made the HMTD and was the owner of the fuses found in the garage. He explained that he formerly belonged to an engineering club at the University of South Florida and had used the HMTD to "boost homemade rockets and send balloons into the atmosphere for testing," according to the complaint.
"Based on my training and experience, HMTD is too energetic and volatile for these types of uses," an FBI agent noted in the complaint.
Russell also admitted to being a "national socialist" who harbored neo-Nazi beliefs, and said he was a member of a group called the "Atom Waffen" (German for "atomic weapon"), the complaint said. The Southern Poverty Law Centre lists the "Atomwaffen Division" as a hate group that shares "a hatred for Jews and an admiration for Adolf Hitler and Nazis".
Inside a bedroom belonging to Russell, the roommate who had been crying when police arrived, officers found firearms, ammunition and "Nazi/white supremacist propaganda," including a framed picture of Oklahoma City bomber Timothy McVeigh on the dresser.
The FBI obtained a warrant for Russell's arrest for the possession of an unregistered destructive device and the unlawful storage of explosive material. Russell was arrested on Monday in Key Largo, according to the Tampa Bay Times, who first reported the story.
Lyssa Himmelman, the sister of one of the slain roommates, told the newspaper that her slain brother had intended to move out "because of how extreme Devon was being." She described Jeremy Himmelman as "a wonderful guy with a good heart" who loved animals and hiking and decried Arthurs's claim that all four men in the apartment were neo-Nazis as "lies".
A representative for the FBI field office in Tampa did not immediately respond to email inquiries Tuesday.
The Tampa Bay Times also identified Russell as a member of the National Guard; a spokeswoman told the newspaper that she was unsure whether there would be a separate investigation of Russell outside of the FBI's.
Arthurs is being held without bail at the Hillsborough County Jail on two counts of first-degree murder, two counts of aggravated assault and three counts of armed kidnapping, according to arrest records. His court hearing is scheduled for tomorrow.
