Texas: Austin explosions: ‘Serial bomber’ hunted after tripwire sets off 4th blast

nbcnews.com - The fourth explosion in less than three weeks in Austin, Texas, appears to be the work of a serial bomber, officials said Monday.

Authorities warned that the devices appear to be getting more sophisticated and asked residents of one neighborhood to stay indoors until 2 p.m. local time (3 p.m. ET) Monday.

"We are clearly dealing with a serial bomber," Austin Police Chief Brian Manley said, adding that he was unable to answer questions from reporters about whether the incidents should be considered domestic terrorism. "We will have to determine if we see a specific ideology behind this."

The latest blast occurred Sunday just after 8:30 p.m. local time (9:30 p.m. ET), when two bicyclists received non-life-threatening injuries after apparently setting off a tripwire in the southwest of the city. The previous three recent explosions had instead been left at people's houses.

The FBI has sent 350 special agents to the Texas capital as well as extra bomb squads.

"With this tripwire, this changes things," said Christopher Combs, special agent in charge of the FBI's San Antonio division. "It's more sophisticated, it's not targeted to individuals ... a child could be walking down a sidewalk and hit something."

The two latest victims, white men ages 22 and 23, set off the bomb that had been left next to a fence and were recovering in the hospital with "significant injuries," Manley said.

Overnight, authorities warned that they didn't want residents in the Travis County neighborhood to leave their homes until 10 a.m. local time to give teams a chance to secure the scene in daylight. Manley later extended that until 2 p.m. citing "an overabundance of caution as we process the scene."

Manley also asked the community to contact authorities if anything looked suspicious or out of place, and cautioned against approaching suspicious items, including boxes and bags.

The unsolved package bombings earlier this month killed two and injured two others. Officials are examining whether the packages have been specifically meant to target minorities: Stephen House, 39, was killed on the morning of March 2, and Draylen Mason, 17, died on the morning of March 12. Both were black members of the same church, Nelson Linder, the local NAACP chapter president, told NBC News last week. ContinueReading