AUSTIN, Texas — The Texas capital was on edge Monday after a spate of package bombings left two Austin residents dead and two others badly wounded.
The latest victim was a 75-year-old woman who was in critical but stable condition with “life threatening injuries” after the package she found outside her home exploded in her arms, Austin Police Chief Brian Manley said Monday afternoon.
That woman was hurt just hours after a 17-year-old boy was killed and another woman was injured by another deadly delivery, Manley said.
Both cases bear “similarities” to the death of Stephan House, 39, who was killed on March 2 by a package bombing that was delivered to his Austin home, Manley said.
"This again, in the third in what we believe to be related incidents that have occurred over the past 10 days," Manley said. "They are not ringing doorbells. Residents are coming out of their homes and finding them on their doorsteps."
Manley said it was too soon to say if it was the work of "a serial bomber."
"But there have been a pattern of incidents," he said. "These are powerful bombs."
So far police have not determined a motive, Manley said, but they are not ruling out the possibility that these could be hate crimes. The most recent victim was Hispanic, and the other three victims were black.
"We are not ruling anything out," Manley said.
Also, the dangerous packages were not delivered by the U.S. Postal Service, officials said.
"If you have a package show at your home and you’re not expecting one, call 911," Manley said. "The three incidences have all occurred at residences. It is important that people be aware."
That goes for the thousands of people currently attending the South by Southwest music, film and technology festival in Austin, Manley said.
But many of the SXSW attendees interviewed by NBC News were unaware of what was happening elsewhere in the sprawling city.
Festival volunteer Kendra Shaw said she hadn’t heard of the bombings or received any notifications from organizers.
"We don’t want everyone to start freaking out," she said. "I feel like South by Southwest has done a better job over the years of handling those things."
Jessica Stratton, who was attending the festival, said she saw TV reports about the bombings. "It seemed to be a nonfestival-related incident so I instantly relaxed," she said.
SXSW ratcheted-up security four years ago after a driver ploughed through a barricade and mowed down festival-goers, killing four of them.
The three blasts all happened in different parts of east Austin, and House’s death was initially investigated as suspicious, Manley said. It’s now officially a homicide, he said.
The FBI and investigators from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives were assisting the Austin Police Department in the investigation, said Special Agent Michelle Lee, from the FBI's San Antonio office.
Abbruzzese reported from Austin, and Siemaszko from New York City.