A former neo-Nazi who converted to Islam killed his two roommates – who were white supremacists – after they disrespected his religion, say police.

Devon Arthurs, 18, from Tampa, Florida, allegedly killed Jeremy Himmelman, 22, and Andrew Oneschuk, 18, before he was arrested on Friday (19 May) after holding three people hostage in a nearby shop.

A criminal complaint says that investigators also found a cooler full of explosive material and other bomb-making materials in Arthurs' apartment in the Hamptons at Tampa Palms complex, which may have belonged to a fourth resident of the property.

The report says that: "Arthurs claimed that he and his roommates shared a common neo-Nazi belief, until Arthurs recently converted to Islam. He said his roommates disrespected his Muslim faith."

The alleged killer also reportedly held two customers and an employee of Tampa's Green Planet Smoke Shop hostage with a semi-automatic pistol asking a customer, "Why shouldn't I kill you?" before being urged to surrender by police.

After leading police to his home, the two dead men were discovered with gunshot wounds to the upper body and head, police said.

The Tampa Bay Times reported that when police arrived at the address they found another roommate, Brandon Russell, who was "crying and visibly upset".

According to a police complaint Russell has also admitted being a neo-Nazi and while searching the garage of the apartment, investigators found a cooler full of a white explosive material known as HMTD, or hexamethylene tiperoxide diamine.

Police also found explosive precursors including potassium chlorate, potassium nitrate, nitro methane and more than a pound of ammonium nitrate in a package addressed to Russell, the report says.

The complaint added that officers found empty 5.56 caliber ammunition casings with fuses that could be used to detonate destructive devices that could be used to make a bomb.

It was reported that Russell had a framed photo of right-wing terrorist Timothy McVeigh in his bedroom and claimed to be from the neo-Nazi group Atom Waffen.

According to his federal arrest affidavit, Russell said the materials were for an engineering project from 2013.

Russell has been charged him with possessing an unregistered destructive device and unlawful storage of explosive material.

Arthurs faces two counts of murder, two counts of aggravated assault and three counts of armed kidnapping. Both are still in custody.