AUSTIN — Residents in southwest Austin were asked to hunker down in their homes overnight after an explosion possibly set off by a tripwire rocked the area Sunday and injured two men.
Authorities worked to determine if the blast was another in a string of bombings that have left multiple people dead and wounded in the Texas capital. A manhunt was underway for the bomber.
The two men were hospitalized with serious, but non-life-threatening injuries, Austin-Travis County EMS said.
Austin Police Chief Brian Manley wouldn't say whether the explosion was linked to the string of package bombs that have fueled fears for more than two weeks.
"It is very possible that this device was a device that was activated by someone who was either handling, kicking or coming into contact with a tripwire," Manley said. "That changes things."
Manley said authorities previously had warned residents not to handle unidentified or suspicious packages. Now residents must have an "extra level of vigilance" and not even approach them, he said.
Dozens of law enforcement officers, including FBI agents, flooded the neighborhood of single-family brick homes to investigate after the reported blast about 8:30 p.m. CT.
Neighbors reported homes rattling after the explosion. One of those injured had nails in their leg, according to KVUE-TV.
Manley urged residents within a half-mile of the blast on Dawn Song Drive to stay inside until at least morning so law enforcement could clear the area. He said a backpack was found and authorities were working to deem it safe.
He didn't offer any details on the explosion or whether it was tied to any of the other incidents.
“We simply don’t know a lot at this point,” Manley said. “Stay in your residence. Don’t touch anything that looks suspicious.”
Earlier Sunday, Manley held a televised news conference and made a plea to the person behind the attacks.
"We hope this person or persons is watching and will reach out to us before anyone else is injured or anyone else is killed," he said. "We assure you, we are listening and we want to understand what brought you to this point, and we want to listen to you, so please call us."
Manley also announced a reward was increased to $100,000 for information that leads to an arrest in the case. That, along with an award from the governor's office, would bring the total reward to $115,000.
Each of the attacks have been similar: a plain cardboard box with standard shipping labels is left on a doorstep.
Each had a bomb inside.
Two people have been killed in the attacks and another two injured. If Sunday's incident is tied to the string of attacks, it would make the fourth bombing in a little more than two weeks.
Police initially raised the possibility of a hate crime because victims in the first two explosions were black. The third apparent target was Hispanic, so it's not clear whether that pattern is intentional because a motive is still unknown.
The first package exploded March 2, killing Anthony Stephan House, 39, when he picked up a package on the front porch of his north Austin home.
The second bomb went off before 7 a.m. on March 12 inside a home in east Austin. Police said Draylen Mason, 17, brought the package inside the kitchen and was opening it alongside his mother when it exploded.
Mason died, and his mother was hospitalized.
The third blast came a short time later in a neighborhood south of downtown. A 75-year-old Hispanic woman picked up a package on her front porch when it exploded, seriously injuring her. Manley said she remains hospitalized with "life-threatening injuries" and authorities are not publicly identifying her.
Manley said this type of investigation and the number of resources on it is "unprecedented" in Austin's history. He said investigators know the incidents were meant to send a message but are unsure what it is.
The explosions occurred in Austin as the popular South By Southwest festival, which attracts global leaders in business, technology, music and film, is occurring in the city and children in Texas public schools are on spring break.
More than 50 agents from the FBI, ATF and other agencies are assisting in the investigation.
“There are agencies at all levels of government that are out here and involved right now,” Mayor Steve Adler told KVUE-TV.