WINTHROP (CBS) — “Hate has no home here,” says a sign at the scene in Winthrop where suspected gunman Nathan Allen began his killing spree Saturday. Suffolk District Attorney Rachel Rollins held a news conference late Monday afternoon, assuring the community that Allen did not appear to be working with a larger group that would continue to pose a threat.

“This person had some very disturbing beliefs,” she said. “White supremacist beliefs regarding members of our Jewish population, as well as Black individuals.”

READ MORE: 'Mecca Of Rowing': Head Of The Charles Regatta Participants Grateful For Event's Return

Investigators say Allen slammed into a building with a truck he stole, then shot and killed Air force veteran Ramona Cooper before turning the gun on retired Massachusetts State trooper David Green, who was also a military veteran.

“He was just a good, kind-hearted person,” said the 58-year-old Green’s brother, Aria Ray Green. “He heard there was an accident, he went to investigate, see if he could help, which is something he would readily do. He was just a very, very good person, and he spent his life serving the community,” he said.

READ MORE: Boston Mayoral Candidates Hit The Streets On First Day Of Early Voting

Cooper was a 60-year-old who worked with other veterans for years after her own military service. Her son Gary Cooper was troubled by the news that she may have been targeted because she was Black. “I got sick to my stomach when I heard it was racially motivated,” he said.

Back at the scene where it all started on Shirley Street, neighbor Toni Cutrone put a bouquet of flowers on the fence. “Their family has such a wonderful reputation, and it’s just a sin. It’s wrong,” she said about Green’s family. “They were all so nice, and you know, my town, this is my town, we should never have to worry about that.”

MORE NEWS: Body Of Missing Five-Year-Old Elijah Lewis Believed To Be Found In Abington

Winthrop Police shot and killed Allen in a confrontation Saturday. DA Rollins said she now feels confident “the threat has been neutralized.”

Christina Hager