The Austin bomber's motive for terrorizing the Texas capital remains a mystery a day following his death -- even after police revealed he'd recorded a 25-minute confession.
Mark Anthony Conditt recorded the confession and then died after a final explosion in an encounter with police early Wednesday, ending the wave of bombings that terrorized Austin for weeks.
But the evidence that investigators have gathered has given them few, if any, clues as to what motivated the 23-year-old man to embark on his spree of violence.
"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 said of the video.
"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."
Questions remain, too, about what Conditt's intentions were beyond Wednesday, had he lived. Authorities who've searched his home said they've found no other finished bombs, but Austin police asked the public Thursday to "remain vigilant and report anything suspicious."
A confession video
The 25-minute recording was found on Conditt's cell phone when police recovered his body Wednesday morning.
In his confession, Conditt described the components of seven bombs he built -- including, authorities believe, the one he used to kill himself -- and detailed the differences among the devices, Manley said.
But the video failed to shed light on a possible motive.
He did not make any references suggesting involvement with terror groups or that the bombings were hate crimes, Manley said.
Search of bomber's house
Federal agents searched the home that Conditt shared with at least two people.
SWAT vans, robots and dozens of officers in tactical uniforms flooded the streets of Pflugerville, a suburb of about 50,000 people north of Austin.
Inside a room, agents found components for making similar bombs to the ones that exploded in the past new weeks, said Fred Milanowski, special agent in charge for the Bureau of Alcohol, Tobacco, Firearms and Explosives' Houston office.
Agents did not find any finished bombs, Milanowski said.
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 "mouse trap" switches and others had "clothespin" switches, the source said.
Frank Alvarado and his two children were among those asked to evacuate homes and businesses within five blocks of Conditt's home as agents removed explosives.
"You would never think it's going to happen over here because everything was happening down south," Alvarado told CNN affiliate KXAN. "You never think it's this close to home -- I'm just two blocks away."
Pink gloves, receipts led police to suspect
Knowing that all the bombs were made from common household items, investigators hit area stores, scanning receipts and looking for suspicious purchases.
The search provided authorities with enough evidence to consider Conditt a "person of interest." Then surveillance footage from a FedEx store south of Austin captured a man in a baseball cap, blond wig and pink gloves bringing two packages to the store.
"Police say that they used that as the final piece to put all of this together, really in the past 24 hours," Tony Plohetski, an investigative reporter for the Austin American-Statesman, told CNN's "New Day."
Investigators used cell phone technology Tuesday night to track Conditt to a hotel in Round Rock, about 20 miles north of downtown Austin. There, they spotted his vehicle.
Police and federal agents gathered outside the hotel but didn't move in immediately. They wanted to wait for backup because they were dealing with a suspected serial bomber.
They were awaiting the arrival of those teams when, some time later, Conditt took off in his vehicle. Police followed him as he drove on a service road along Interstate 35 until he stopped on the side of the road.
As a SWAT team cautiously approached, Conditt detonated a device inside his red SUV and died in the blast.
Questions for his roommates
Conditt's two roommates were detained and questioned by police as investigators tried to determine if he acted alone. Police said one of the roommates was released Wednesday and one was free to go on Thursday.
They were not arrested, and neither roommate was publicly identified.
Jennifer Withers said her son moved to Conditt's three-bedroom home after a friend told him about a room for lease.
In the three months that her son has lived at the Pflugerville house, Withers said she never saw Conditt and that her son didn't express any concerns.
"Nothing seemed out of the ordinary," she told KXAN. "We didn't suspect anything. He didn't suspect anything."
- Feds tracked Austin bomber after FedEx camera got his plate, congressman says
- FedEx driver's patriotic act caught on camera
- What we know about the Austin serial bomber
- Police: Austin bomber left 25-minute confession video on phone
- Austin bomber showed no remorse in confession video, lawmaker says
- Austin bomber's roommate still being questioned, lawmaker says
- FedEx is hiking rates again
- 'Plate Man' convicted for getting Missouri residents Illinois plates
- Bomber's Tactics Studied for Clues
- Explosión en un FedEx cercano a San Antonio, Texas, podría estar vinculado a estallidos de Austin