Austin police said Conditt left a 28-minute audio "confession" recorded on a cell phone hours before he died after detonating one of his devices in his car.
In the audio, Conditt admitted that "I wish I were sorry but I am not."
So far, authorities are not saying what specific contents were on the recording but law enforcement sources familiar with the investigation leaked bits and pieces of the statement, according to the American-Statesman.
Conditt is reportedly heard describing himself in the recording as a "psychopath" who has been mentally ill since childhood. He is also reportedly heard saying that if he feels police are close to arresting him, he would end his life by blowing himself up inside a crowded McDonald's.
He reportedly blamed himself for tipping off investigators as to his whereabouts; he entered a FedEx store and shipped one of the parcels using an alias. In his recording, he reportedly says he realized it was a mistake, because it allowed surveillance cameras to see him as well as his license plate.
He can also reportedly be heard saying that his actions resulted in deaths and families losing loved ones as well as injuries.
No clues were offered as to why Conditt sent the bombs.
"It is the outcry of a very challenged young man talking about challenges in his life that led him to this point," Interim Austin Police Chief Brian Manley told reporters on Wednesday night. "I know everybody is interested in a motive and understanding why. And we're never going to be able to put a (rationale) behind these acts."
Earlier Thursday, it was learned Conditt had been part of a Christian survivalist group that would discuss weapons and dangerous chemicals. Authorities also said he had a target list of future locations.
As a teenager, Conditt took part in the conservative club called Righteous Invasion of Truth (RIOT), which involved home-schooled youth studying the bible and being taught gun skills.
Manley said that Conditt's confession made no reference to any terror groups or hateful ideologies.
At the time of his death, he was an unemployed college dropout who bought bomb-making materials at Home Depot.0comments
Federal agents also went to Conditt's home on Wednesday, hoping to find any other explosives the 24-year-old may have left behind. Police interviewed Conditt's roommates, trying to discern whether the killer was working alone. Neither of the roommates were arrested.
Parts of Conditt's hometown, Pflugerville, Texas, were evacuated early in the morning, though police didn't elaborate on why. CNN spoke to Fred Milanowski, the ATF's special agent in charge, who said that components for making the bombs were found in one room of Conditt's home. However, no functional explosives were found, and all of the materials were confined to one room.