At 1:30 a.m., Manley said it was possible that a trip-wire triggered the explosion, a departure from the three prior bombs that were all inside packages. Manley said investigators believe Sunday's explosion was caused by a bomb and are operating under the assumption that it was connected to the three prior blasts.
>> Read more trending news
Some neighbors reported they had been told the explosion was the result of a trip wire, but police would not confirm any details of the blast Sunday night.
Two men in their 20s were hospitalized with serious injuries, but officials said later that they were in good condition.
If Sunday’s blast is connected to the three bombs that have killed two Austin residents and injured two others since March 2, it would mark a geographic widening of the bomber’s targets. The first three bombs were east of Interstate 35 and hit black or Hispanic residents. The first two victims, 39-year-old Anthony Stephan House and 17-year-old Draylen Mason, are connected to two prominent African-American families with ties to an East Austin church and long histories fighting for racial justice and empowerment of the city’s African-American community. The third bomb hit a Latina resident and her mother in Montopolis.
For many worried Austinites, the bombings raised the specter that someone was targeting minority residents and police have said they are probing the family connections between the victims. The race of the victims Sunday night were not released.
Angie Wagner, a Travis Country homeowners association board member who lives in the area of Sunday night’s explosion, said the neighborhood is a quiet, close-knit community.
“This will cause everyone to keep a closer eye on things,” she said. “We just started a community watch program, and they’re about to start their training.”
Russell Reno has lived in the area for about six months. He said a big reason why he chose to move into the neighborhood from Buda was because it was a relaxed and family-oriented.
He said he had heard about explosions in other parts of the city and was perplexed why someone would target his neighborhood.
“There are some sick people in the world,” he said.
It’s not clear if the fourth device was left at someone’s door as in the first three instances.
Police have said that whoever constructed the first three bombs used common household items that can be easily purchased at hardware stores, potentially making efforts to identify the perpetrator more difficult, law enforcement officials said last week.
Federal agents this week have been visiting local stores trying to determine if a customer purchased items that appear suspicious, but have not gained information to lead them to a possible suspect, sources have said.
Even before Sunday night, the bombings had put Austin on edge as it hosted the massive South by Southwest festival. Austin police have responded to about 700 suspicious package calls, and Manley said earlier Sunday that more than 500 federal agents are assisting the Police Department in the investigation, including officials from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives. Authorities have followed up on 435 leads that led to 236 interviews.
A bomb scare led to the cancellation of a highly anticipated SXSW showcase by the Roots on Saturday night. Later that night, a 26-year-old man was arrested and charged with emailing the threat that led to the concert. Trevor Weldon Ingram faces up to 10 years in prison on charges of making a terroristic threat, but police said they do not think he is connected to the earlier bombings.
On Sunday, police announced a $50,000 increase to the reward offered in exchange for any information leading to the arrest of the bomber behind three recent deadly explosions.
The increase, on top of $15,000 being offered by Gov. Greg Abbott and the $50,000 reward offered by police last week, brings the total reward amount to $115,000.
Police also said that they believe the incidents were intended to send a message and continued to plead for any information from the community.
“We don’t know what the ideology is behind this or what the motive is behind this,” Manley said.
– This article includes reports from Brandon Mulder, Mark D. Wilson, Tony Plohetski, John Bridges and Tom Labinski.
What You Need to Know: Austin Package Explosions