TEXAS, USA (AP) — The suspected Austin bomber called himself a “psychopath” in a recorded confession and said he felt no remorse for deadly explosions that killed two people and terrorised the city, a US congressman said Saturday.

Investigators are still looking into what motivated 23-year-old Mark Anthony Conditt, but the recording he left on his cellphone shows that he was a “sick individual”, US Rep Michael McCaul said.

“He did refer to himself as a psychopath. He did not show any remorse, in fact questioning himself for why he didn’t feel any remorse for what he did,” McCaul said.

Conditt makes no mention of a racial motivation on the recording, but investigators are still looking into that as a possibility, he said. The first three victims were minorities.

McCaul, a former federal prosecutor who chairs the House Committee on Homeland Security, spoke at a news conference where he thanked law enforcement officials for bringing the three-week spree to an end. He called the investigation, which included more than 800 officers, a textbook example of how local, state and federal agencies should work together.

Beginning March 2, police said, Conditt planted bombs in different parts of Austin, killing two people and severely wounding four others. He began by placing explosives in packages left overnight on doorsteps, killing 39-year-old father Anthony Stephan House and 17-year-old musician Draylen Mason and critically injuring 75-year-old Esperanza Herrera. He then rigged an explosive to a tripwire along a public trail, injuring two young men who crossed it. Finally, he sent two parcels with bombs via FedEx, one of which exploded and injured a worker at a distribution centre near San Antonio.

Conditt died after detonating an explosive device early Wednesday as SWAT team officers ran toward his vehicle to arrest him in an Austin suburb. Investigators discovered a roughly 25-minute recording that Conditt had made on his cellphone allegedly confessing to the crimes.

Interim Austin Police Chief Brian Manley said the department will continue withholding the recording from the public as investigators look into Conditt’s motive and whether anyone else was involved. He noted that Conditt’s two roommates have been questioned and said that several more people will be interviewed.

Releasing the recording now could jeopardize any future prosecutions, although no one else has been arrested or charged, Manley said.

The identification of Conditt as the bomber continued to baffle residents in Pflugerville, the Austin suburb where Conditt had been home-schooled and grew up in a Christian family.