(CNN) -- Mark Anthony Conditt, who police say was behind a wave of bombings in Austin and south-central Texas, killed himself early Wednesday in what investigators described as an explosion inside his car, leaving them scrambling to determine whether any bombs remain and if he acted alone.
Conditt detonated a bomb in his vehicle before dawn on the side of Interstate 35 in Round Rock, north of Austin, as police approached him, authorities said.
Police had come to believe Conditt was responsible for five explosions that killed two people and injured five others in Austin and the San Antonio area beginning March 2, and an arrest warrant was issued for him Tuesday night.
Authorities tracked Conditt to a hotel in Round Rock after reportedly identifying him using receipts, internet searches, witness sketches and, ultimately, surveillance video that revealed he'd delivered packages days earlier to an area FedEx store, officials said.
Authorities were outside the hotel early Wednesday when Conditt got in his vehicle and drove away, police said. They followed him. That's when he pulled into a ditch and blew himself up, police said. The blast injured a SWAT officer.
Even in announcing his death, though, police warned a wary public not to let down their guard.
"We don't know where this suspect has spent his last 24 hours, and therefore we still need to remain vigilant to ensure that no other packages or devices have been left throughout the community," Austin police Chief Brian Manley said.
• Police don't yet "understand what motivated (Conditt) to do what he did," Manley said, adding, "This investigation is still underway, so we cannot say that this was individual acting on their own."
• Conditt, 23, lived in Pflugerville, a city just outside Austin, according to public records and a longtime neighbor of his parents.
• Officers detained and questioned his two roommates Wednesday. Neither person was under arrest, Austin police said.
• An arrest warrant for Conditt and a criminal complaint charging him with one count of unlawful possession and transfer of a destructive device were filed Tuesday night, authorities said. An affidavit detailing the reasons for the warrant and charge is under seal, they said.
• An aunt of Conditt's said her family is "devastated and broken at the news that our family could be involved in such an awful way."
• People were evacuated Wednesday morning from parts of downtown Pflugerville, police said, without elaborating. In a video, Pflugerville Mayor Victor Gonzales noted a heightened presence of police and said, "This is a fluid situation, and information is limited at this time."
• Austin police on Wednesday morning conducted a "follow-up investigation" at the FedEx facility where an intact bomb was found a day earlier, the agency tweeted. The building was temporarily evacuated, but police said normal business "will resume."
• Conditt was an Austin Community College student from 2010 to 2012 but did not graduate, the school said.
Conditt blew himself up as police approached, police say
The bombings -- five over nearly three weeks, with some involving packages left on Austin doorsteps -- had driven the area to near-panic.
But by Tuesday night, investigators had identified a suspect and found his vehicle at the Round Rock hotel, about 20 miles north of Austin, Manley said.
While police waited for tactical teams to arrive, Conditt drove away, then stopped in a ditch off I-35, Manley said.
As SWAT members approached the vehicle, Conditt "detonated a bomb inside the vehicle, knocking one of SWAT officers back." The blast killed Conditt and injured the officer, Manley said.
A different SWAT officer fired a gun at Conditt, Manley said; it wasn't immediately clear whether Conditt was shot.
Video and an intact package may have helped ID Conditt
Video of a man dropping off two packages Sunday at a location described by CNN affiliate WOAI as a FedEx store south of Austin appears to have played a major role in helping investigators identify Conditt.
The surveillance images show a man wearing gloves, a black T-shirt and a cap taking two packages into the shop. WOAI published the surveillance images, and Austin Mayor Steve Adler told CNN that police believe the person in the images was responsible for the Texas bombings.
Police haven't explicitly said what happened to the packages in that video. But early Tuesday, in the last known explosion before Conditt killed himself, a package exploded on an automated conveyor at a FedEx sorting center near San Antonio, slightly injuring a worker there.
Also Tuesday, an unexploded package bomb was discovered at another FedEx facility near Austin.
"Police say that they used that (video) 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."
FedEx said it provided authorities with "extensive evidence" from its security system on the packages and the person who shipped them.
The bombs: Design and materials
The unexploded bomb intercepted Tuesday will have provided a gold mine of clues, including materials used in the bombs and possibly DNA from the attacker, a federal law enforcement source involved in the Austin investigation told CNN.
Investigators believe the same person is behind all the explosive devices, the source said, adding that the devices are similar in design and use the same components, including a "mouse trap" or a "close pin" switch, according to the source.
The level of bombmaking skill doesn't necessarily point to military experience, the source added.
Citing a high-ranking law enforcement official, Plohetski, the Austin reporter, said investigators found common household ingredients in the bombs, so police hit area stores, scanning receipts and looking for clues.
"Agents fanned out throughout the city of Austin, going to big-box retail stores as well as locally owned stores trying to determine whether or not there were suspicious purchases," Plohetski told CNN. They were "going through receipts and going through sales records from those stores."
The first three explosions in Austin involved cardboard packages left in front yards or on porches. The parcels weren't delivered by the US Postal Service or services such as UPS or FedEx, police have said.
Those blasts -- one on March 2 and two more on March 12 -- killed or wounded three African-Americans and one Hispanic woman. They happened in east Austin areas where most residents are minorities, and some there expressed concern the attacks might have been racially motivated.
The first explosion killed Anthony Stephan House, 39; the second killed Draylen Mason, 17; and the third critically injured a 75-year-old woman. Police have not ruled out the possibility that those bombings could be hate crimes.
In the fourth blast, on Sunday, a device was triggered by a tripwire, injuring two white men in an area where most residents are white.
The fifth explosion happened early Tuesday at the FedEx sorting facility near San Antonio.
Conditt's family 'devastated'
One of Conditt's aunts released a prepared statement Wednesday, saying his relatives were "devastated and broken at the news that our family could be involved in such an awful way."
"We had no idea of the darkness that Mark must have been in," the statement reads. "Our family is a normal family in every way. We love, we pray, and we try to inspire and serve others.
"Right now our prayers are for those families that have lost loved ones, for those impacted in any way, and for the soul of our Mark. We are grieving and we are in shock. Please respect our privacy as we deal with this terrible, terrible knowledge and try to support each other through this time."
This story has been updated to correct Mark Anthony Conditt's age to 23, based on public records. Earlier, police identified the suspect as a 24-year-old man.
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