Two Black people, an Air Force veteran, and a retired Massachusetts state trooper were shot dead after an intentional car crash near Boston over the weekend in what the district attorney is now calling an incident of “extremism and white supremacy,” according to a statement from District Attorney Rachael Rollins.

She said she believes race was a motivating factor in the deaths of retired state trooper Dave Green and Air Force veteran Ramona Cooper, who are both Black.

Green, a 58-year-old retired Massachusetts State Police trooper, and Cooper, a 60-year-old staff sergeant in the Air Force who stayed involved in the military, were killed after a gunman slammed a stolen truck into a house and another vehicle in the Winthrop neighborhood and then shot them.

The gunman, 28-year-old Nathan Allan, was later killed by police, according to the Suffolk District Attorney.

All three dead are Winthrop residents.

“This is a sad day,” Suffolk County District Attorney Rachael Rollins said. “These two people protected our rights, they fought for us to be safe and to have the opinions that we have, and they were executed yesterday. And we will find out why and find out more about this man who did this.”