Austin Police plead with serial bomber: We hope you are watching and will call us

Christal Hayes | USA TODAY

Show Caption Hide Caption Police search for motive in Austin bombings Three package bombs left on doorsteps have exploded in less than two weeks in Austin, killing two people, wounding two others and leaving investigators searching for any possible explanation or motive. All of the victims were minorities. (March 13)

Austin Police sent a message Sunday to the person behind a string of deadly bombings that have rocked the city: We are listening and want to talk.

More than two weeks have passed since the first bomb went off in the Texas capital. Since then, there have been two other bombs and hundreds of tips to police, but so far no suspects or arrests, leaving the city on edge.

Austin Police Chief Brian Manley 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.

Manley pleaded during a Sunday afternoon news conference to those responsible. "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," he added.

Manley said investigators know the incidents were meant to send a message but are unsure what it is. He said hundreds of officers are investigating, more than 400 leads are being followed, and more than 200 interviews completed, but police haven't been able to piece together who is behind the string of attacks.

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He said this type of investigation and the number of resources on it is "unprecedented" in Austin's history.

All three bombs were placed on doorsteps in plain cardboard boxes, so police have encouraged residents to call authorities if they see an unexpected box on their doorstep.

Two people were killed and two others were injured. 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.

Manley said a motive is still unclear and investigators don't want to limit the investigation in one direction.

The first package exploded on March 2, killing Anthony Stephan House, 39, when he picked up a package on the front porch of his northern 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 Austin. A 75-year-old Hispanic woman was picking 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 investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives have examined all three explosives and found the materials used are highly dangerous and hard to keep stable.

He said investigators now know much more about how the devices were constructed, adding they pose an "ongoing hazard" to anyone in the area.

The bombings come as the city hosted the annual South By Southwest festival, which attracted global leaders in business, technology, music and film. Festival organizers issued a statement that they were "heartbroken" by the explosions and urged attendees to keep an eye out for any suspicious behavior.

A concert at the festival was canceled Saturday evening after an unrelated bomb threat. That person was arrested, but police say the suspect was not tied to the package bombs.

Contributing: Rob Pegoraro and Alan Gomez

Follow Christal Hayes on Twitter: Journo_Christal.