AUSTIN, TEXAS (REUTERS) - The man accused of carrying out a three-week bombing spree that killed two people in Texas before blowing himself up as police closed in on him was a 23-year-old unemployed man from suburban Austin, authorities said on Wednesday (March 21).

Federal prosecutors said on Wednesday they had charged Mark Conditt of Pflugerville, Texas, with unlawful possession and transfer of a destructive device prior to his death on the side of a highway.

In addition to killing two, the bombings that began on March 2 injured at least five people and left Austin, a fast-growing city of one million people, on edge as the bomber moved from parcels left on doorsteps to one activated by a trip wire to at least two sent via FedEx.

Police tracked Conditt to a hotel about 32km north of Austin and were following his vehicle when he pulled to the side of the road and detonated a device, killing himself, Austin Police Chief Brian Manley told reporters near the scene.

"The suspect is deceased and has significant injuries from a blast that occurred from detonating a bomb inside his vehicle," Manley told reporters.

Police began searching Conditt's house in Pflugerville, though Texas Governor Greg Abbott said it would be a time-consuming process as they were worried it could be booby-trapped, the Austin American-Statesman newspaper reported.

Pflugerville police earlier ordered the evacuation of homes in a five-block radius around the house where Conditt lived with two roommates. Police were questioning the roommates but did not regard them as suspects, Abbott told Fox News.

Law enforcement officials warned area residents to remain cautious, saying they did not know if the bomber had left other devices.

Conditt did not leave a suicide note or any other documents explaining the reason for the bombings, the American-Statesman quoted Abbott as saying.

Conditt had lived with his parents, William and Danene Conditt, until 2017, when he moved into a house over a kilometre away, public records showed.

In 2013, Danene Conditt posted a photo of a man she referred to as Mark on Facebook and said she home-schooled her children.

"I officially graduated Mark from High School on Friday. 1 down, 3 to go. He has 30 hrs of college credit too, but he's thinking of taking some time to figure out what he wants to do ... maybe a mission trip," she said in the photo caption.

Conditt's aunt released a statement on behalf of the family, CNN reported.

"We are devastated and broken at the news that our family could be involved in such an awful way," the network quoted the statement as saying. "We had no idea of the darkness that Mark must have been in."

Reuters could not reach family members.

'PARTYING PRETTY LATE'

Jay Schulze, a 42-year-old network engineer, said he lived a few houses away from the bombing suspect, who with his friends would relax late at night.

"They would be out in back playing music and partying pretty late," Schulze said.

While jogging on Tuesday night, Schulze noticed a heavy police presence in the area, with drones flying overhead. He said he was stopped briefly by a person who he thought was an FBI agent.

Manley said Conditt was believed to be responsible for six bombs around Austin and in Schertz, near San Antonio, including one that did not explode.

The first three were parcel bombs dropped off in front of homes in the Austin area. A fourth went off on Sunday night, apparently detonated with a trip wire around Austin, and a fifth exploded inside a FedEx Corp facility in Schertz on Tuesday.

FedEx officials provided "key evidence" that led to the suspect's identification, the company told employees in an internal memo seen by Reuters on Wednesday.

The first two bombs killed Anthony Stephan House, 39, and Draylen Mason, 17. The fact that both men were black raised fears they were part of a hate crime, but investigators said the blasts that came later seemed to target more random victims.