Investigators have found the gunman who killed two people Saturday in Winthrop, Massachusetts, had made "some troubling white supremacist rhetoric" that targeted Black and Jewish people, and both his victims were Black, officials said Sunday.
The shooting is now being investigated as a hate crime, according to Suffolk County District Attorney Rachael Rollins.
The gunman "walked by several other people that were not Black and they are alive. They were not harmed," she said.
The man, whom she identified as 28-year-old Nathan Allen, was quickly killed by police officers. They were arriving to the scene for what they thought was a traffic accident -- the man crashed a stolen plumbing truck into a building, injuring two other people in the process, before he opened fire on the two people.
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"This is a sad day. These two people protected our rights. They fought for us to be safe," Rollins said.
PHOTOS: Police, Rescue Response to Winthrop Shooting
The rampage erupted in quiet Winthrop, a small city across Boston Harbor from Boston Logan International Airport, before 3 p.m. Rollins said the gunman was driving the stolen truck at twice the speed limit before he crashed it, and she speculated that the man may have been trying to reach Jewish temples in the area.
"He had anti-Semitic rhetoric written in his own hand," she said.
But after the crash, he appeared to target Black people. The Air Force veteran, Ramona Cooper, was shot three times in the back, while the retired state trooper, David Green, was "executed," shot four times in the head three in his torso, according to Rollins.
Rollins had no knowledge of the gunman before the attack. He had a license to carry firearms, which means he'd passed a background check, she said.
In fact, the man had a Ph.D. and no criminal history, Rollins said in a statement Sunday evening.
"To all external sources he likely appeared unassuming. And then, yesterday afternoon he stole a box truck, crashed it into another vehicle and a property, walked away from the wreckage interacting with multiple individuals and choosing only to shoot and kill the two Black people he encountered," she wrote, noting that racism-driven violence is on the rise in the U.S.
"This individual wrote about the superiority of the white race. About whites being ‘apex predators.’ He drew swastikas," Rollins wrote.
Winthrop police Chief Terence Delehanty said at the news conference that the city has "no tolerance for hate."
The shooting and the gunman's motivation remain under investigation, Rollins said at the news conference. She pointed outthat "this individual will not hurt anyone else," but added, "these families deserve answers."