Austin, Texas CNN  — 

When the Austin bomber went to a FedEx store Sunday to ship two more of his package bombs, he made the mistake of parking within view of a surveillance camera, a US congressman told CNN.

The license plate of Mark Anthony Conditt’s red Ford SUV could be seen on video and police used the images to begin tracking the killer, Rep. Michael McCaul, whose district includes the town where the bomber lived, said Thursday.

Eventually authorities were able to monitor Conditt’s location by pinpointing where his cellphone was being used, McCaul said.

While Conditt’s motive remains a mystery, McCaul said the bomber talked on a 25-minute confession video about his despondence over his difficulty with employment and other “aggravating factors.”

The bomber expressed no remorse for killing two people and wounding five, McCaul said. The congressman said Conditt spoke matter-of-factly.

The bomber had a list of addresses on a device that authorities recovered. The list, McCaul said, has been mischaracterized in media reports as a target list. The congressman said he didn’t know whether they were potential targets or whether the addresses were linked. Law enforcement has cleared those sites, he said.

The bomber bought several “Slow Down Children At Play” signs at a Home Depot, which McCaul thinks means Conditt was planning more attacks using trip wires.

Police tell public to stay vigilant

Conditt recorded what police labeled as a confession the night before he died, as if he knew authorities were closing in on him. He died after a final explosion in an encounter with police early Wednesday, ending the wave of bombings that terrorized Austin for almost three 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 cellphone 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.

Mark Anthony Conditt

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 few 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.

Authorities surround the home of Austin bomber Mark Conditt in Pflugerville, Texas, on Wednesday.

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.

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 explosive materials.

“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.

Investigators used cellphone technology Tuesday night to track Conditt to a hotel parking lot 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 they forced him to stop 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.”

CNN’s Tristan Smith reported from Austin, Texas, and CNN’s Nicole Chavez and Steve Almasy reported and wrote in Atlanta. CNN’s Jamiel Lynch, Doug Criss and Jason Hanna contributed to this report.