Days after the Austin bomber blew himself up as police closed in, investigators are no closer to answering the question nearly everyone in the community is asking: Why?
Investigators searching for a potential motive are relying on Mark Anthony Conditt's own words from a 25-minute recording he made hours before he was confronted by a SWAT team early Wednesday.
In the cellphone recording, Conditt, 23, refers to himself as a "psychopath" and shows no contrition for carrying out a nearly three-week-long bombing spree that left two people dead and spread fear across the city.
"Why would someone do such a senseless act of random violence? To many of us it doesn't make a whole lot of sense," Texas Rep. Michael McCaul said Saturday. "All we really have at this point in time ... are his own words from his confession tape where he describes himself as a psychopath, apparently expressing no remorse for the killings that he committed.
"It's hard to imagine someone whose mind is so sick that they could commit bombings like this and feel absolutely no remorse," McCaul said.
Both McCaul and Austin Police Chief Brian Manley said Conditt does not address race in the recording, but authorities have not ruled anything out as the investigation continues.
The two victims in the bombings were African-American and the first three bombings were carried out in a largely minority area of Austin, prompting fears of a racially motivated killer.
The bomber's mistake
A security camera at a FedEx store south of Austin caught Conditt's red SUV on video, McCaul said.
The bomber went to the store on Sunday and made the mistake of parking within view of a surveillance camera that captured the vehicle's license plates, the congressman said.
Surveillance photos from the mail delivery office in Sunset Valley showed Conditt wearing a baseball cap, blond wig and pink gloves as he brought two packages to the store.
Investigators used cellphone technology to track down Conditt on Wednesday and to confirm that he had been to all of the bombing locations, McCaul said.
His SUV was ultimately found later Wednesday, running in a parking lot of a hotel in Round Rock, Manley said. As plainclothes officers and unmarked vehicles descended on the area and authorities worked to get SWAT, tactical and ballistic teams in place, Conditt pulled out of the lot.
Authorities followed and a SWAT team performed a tactical maneuver to force Conditt to stop the SUV.
Manley praised the officers who confronted Conditt, saying, "they charged up to a vehicle they knew was likely occupied by the suspect in this incident and that he had a bomb with him. And what happened next was chilling to watch as that explosion went off and one of our SWAT officers flew backward and landed on the ground."
The officer was not seriously injured.
Austin's weeks of 'collective fear'
Austin Mayor Steve Adler said the city's "collective fear and anxiety" was growing as the bomber carried out the string of attacks.
"There was feeling that there was not much that we could do. There was a collective helplessness," Adler said Thursday at a City Council meeting.
"Our community was beginning to fray," he added.
Some residents have breathed sighs of relief since Conditt's death, while others remain shaken up.
Narcisa Velasco had rushed to help a friend, a 75-year-old woman who was severely injured on March 12 after picking up a package in front of a southeast Austin home.
She said the sight of the woman's bloody wounds and the chaotic scene of debris from the bomb are still haunting her and her family members, some of whom also witnessed the aftermath of the explosion.
"We are sleeping with all the lights on," she said.
The lives of Anthony Stephan House and Draylen Mason were cut short when explosive packages arrived on their doorsteps.
The first blast on March 2 killed House, a 39-year-old father who worked as a project manager for Texas Quarries.
On March 12, Mason was killed when he brought a package indoors to open it and it exploded, police said. The 17-year-old high school student played bass in a youth orchestra, and was taking college classes.
Both men were African-American. Also among the injured were an African-American woman and one Hispanic woman.
Prior to Conditt's death, authorities believed the bombings could be racially motivated. But police said Wednesday that Conditt did not mention anything in his video confession about terror or hate.
"I know everybody is interested in a motive and understanding why," said Manley, the Austin police chief. "And we're never going to be able to put a (rationale) behind these acts."
In a statement, Mason's family thanked law enforcement, saying they felt that Mason has "received justice."
"The most recent chain of events have brought some sense of closure that our beloved has received justice, and we are prayerful that we can now start to move forward with our lives," said the statement obtained by CNN affiliate KEYE.
Search of bomber's house
Federal agents searched Conditt's home in Pflugerville for almost two days, cautiously removing explosive materials and looking for clues that could point to a reason for the bombings.
Investigators discovered components for making similar bombs to the ones that exploded in the past few weeks, but no finished bombs were found, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.
The devices that exploded in Austin and near San Antonio were pipe bombs with batteries and smokeless powder and were constructed with materials found in a hardware or sporting goods store, a law enforcement source with knowledge of the investigation told CNN.
The bombs had distinctive shrapnel inside. Some had "mousetrap" switches and others had "clothespin" switches, the source said.
Two of Conditt's roommates were detained and questioned by police. One of them was released hours after Conditt's death, but the other was not free to go until the next afternoon, police said.
They were not arrested, and neither roommate has been publicly identified.
Manley on Saturday left open the possibility the roommates could face more questioning as the investigation continues.