The suspect in the deadly bombings that terrorised Austin, Texas, blew himself up as authorities closed in on him, but police have warned that more bombs could be out there.

The suspect’s motive remained a mystery, along with whether he acted alone in the five bombings in the Texas capital and suburban San Antonio that killed two people and wounded four others.

Police zeroed in on the 24-year-old man in the last 24 to 36 hours and located his vehicle at a hotel on Interstate 35 in the suburb of Round Rock.

Officials investigate the scene where a suspect in a series of bombing attacks in Austin blew himself up (Eric Gay/AP)
Officials investigate the scene where the suspect blew himself up (Eric Gay/AP)

Officers were waiting for armoured vehicles to arrive before moving in for an arrest when his vehicle began to drive away, Austin police chief Brian Manley said at a news conference.

Authorities followed the vehicle, which ran into a ditch on the side of the road, he said.

When members of the Swat team approached, the suspect detonated an explosive device inside the vehicle, the police chief said.

The blast knocked one officer back, and a second officer fired his weapon, Mr Manley said.

A law enforcement official identified the dead man as Mark Anthony Conditt.

Authorities released few details about the suspect, except his age and that he was white.

But online postings indicate he was home schooled.

He later attended Austin Community College from 2010 to 2012, according to a college spokeswoman, but he did not graduate.

A blogger who identified himself as Mark Conditt of Pflugerville described his interests as cycling, tennis and listening to music.

In blogs dated from 2012, he wrote that gay marriage should be illegal and called for the elimination of sex offender registrations.

The mayor of Pflugerville, an Austin suburb not far from the site of the first of four bombings, said the suspect lived in his city, just two streets from his house.

Officials at the scene in Round Rock, Texas (Eric Gay/AP)
Officials at the scene in Round Rock, Texas (Eric Gay/AP)

Pflugerville resident Jay Schulze said he was jogging on Tuesday night when he was stopped by police and asked about the bombings.

He said police flew drones over a home for about six hours between Tuesday evening and early Wednesday morning.

Mr Schulze described the home over which the drones were flying as “a weird house with a lot of people coming and going” and a bit rundown.

A neighbour who watched the suspect grow up said he “always seemed like he was smart” and “polite”.

Jeff Reeb said he has lived next to the parents of Conditt for about 17 years and that they are good neighbours.

Mr Reeb said Conditt and his grandson played together when they were younger and that Conditt still visited his parents regularly.

The parents live a few miles from the Pflugerville home where Conditt lived with roommates.

Mr Reeb said Conditt was in the process of gutting the house and remodelling it, which meant a lot of hammers and nails around frequently.

He said police had an unmarked car parked near Conditt’s parents’ house overnight into Wednesday.

Mr Reeb said Conditt’s father, whom he called Pat, worked as an Amway distributor and also bought electronics on the side to resell.

Austin was hit with four package bombings starting on March 2.

A fifth parcel bomb went off early on Tuesday at a FedEx distribution centre near San Antonio.

Citing a high-ranking law enforcement official, the Austin American-Statesman reported that authorities had identified the suspect based largely on information, including security video, gleaned after he sent an explosive device from an Austin-area FedEx store.

Police warned on Wednesday of the possibility that more bombs had yet to be found.

“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 to the community,” Mr Manley said.

Austin police chief Brian Manley, right (Eric Gay/AP)
Austin police chief Brian Manley, right (Eric Gay/AP)

Authorities initially believed the bombings may have been hate crimes because the victims of the earliest blasts were black, but they backed off that theory after Hispanic and white victims from different parts of the city were also affected.

Fred Milanowski, an agent with the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), said it was “hard to say” if the bombing suspect had acted alone.

“What we do know is we believe the same person built each one of these devices,” said Mr Milanowski, the agent in charge of the Houston division of the ATF.

Asked if the suspect built bombs before the Austin attacks, Mr Milanowski said: “We know when he bought some of the components. It’s hard to say whether he was building along the way.”

Austin mayor Steve Adler thanked law enforcement for their work in bringing down the suspect and urged residents to continue to report anything that appeared suspicious or out of place.

Isaac Figueroa, 26, said he and his brother heard sirens and helicopters early on Wednesday in the area and drove towards them, then cut through nearby woods on foot after they hit a police roadblock.

Mr Figueroa said they saw a silver or grey Jeep Cherokee that was pinned between black and white vehicles and “looked like it had been rammed off the road”.

He said he saw police deploy a robot to go to examine the Jeep.

President Donald Trump, who had earlier said whoever was responsible for the Austin bombings was “obviously a very sick individual or individuals”, tweeted: “AUSTIN BOMBING SUSPECT IS DEAD. Great job by law enforcement and all concerned!”

The suspect’s death followed a day of rapid-fire developments in the case.

Early on Tuesday, a bomb inside a package exploded as it passed along a conveyor belt at a FedEx shipping centre in Schertz, north east of San Antonio and about 60 miles south west of Austin.

One worker reported ringing in her ears and was treated at the scene.

Later in the morning, police sent a bomb squad to a FedEx facility outside Austin airport to check on a suspicious package.

Federal agencies and police later said the package had contained an explosive that was successfully intercepted and that it too was tied to the other bombings.

The Schertz blast came two days after a bombing wounded two men on Sunday night in a quiet Austin neighbourhood about three miles from the FedEx store.

It was triggered by a nearly invisible tripwire.