Austin residents are being told to be vigilant about unexpected or suspicious packages at their door after a series of package bombs killed two people and critically injured a woman.
Three package bombs have exploded in the Texas capital over 10 days.
"The evidence makes us believe these incidents are related," Austin police Chief Brian Manley said.
It's not known if the victims knew each other or if they were targeted, he said. Investigators have not discovered a motive, and Manley did not say if anybody has claimed responsibility.
But the explosions have rattled residents who are wary of what Manley described as "box-type deliveries."
The first blast on March 2 killed Anthony Stephan House, 39 and the stepson of Freddie Dixon, a former pastor at a historic black church in Austin, The Washington Post reported. Dixon is friends with the grandfather of the second victim, a teenager who was killed Monday, according to the newspaper.
On Monday, a second bombing killed a 17-year-old black male, A woman also was hurt in the blast, police said. A second explosion on Monday, around noon, severely injured a 75-year-old Hispanic woman.
The rsidents all found the packages outside their houses, but none was delivered by the US Postal Service or delivery services such as UPS or FedEx, police said. Authoritise have not decided if they are hate crimes but said that's considered a possibility because of the victims' races.
The packages were placed in front of the residents' houses, the police chief said. They appeared to be "average-sized delivery boxes, not exceptionally large," Manley said.
The first blast on March 2 that killed House was initially regarded as an isolated incident, but police now classify it as a homicide.
Then Monday, a blast was reported at 6:44 a.m., killing the teenager and injuring a woman.
"One of the residents went out front, and there was a package on the front doorstep," Manley said. "They brought that package inside the residence, and as they opened that package, both victims were in the kitchen, and the package exploded, causing the injuries that resulted in the young man's death and the injuries to the adult female."
The scond blast on Monday happened when the woman found a package on her porch.When she picked it up, it detonated,Manley said.
"These are very powerful devices," he said, declining to be specific. "There's a certain level of skill required to move a device like this."