WINTHROP — The shooting deaths of an Air Force veteran and a retired State Police trooper in Winthrop Saturday are being investigated as hate crimes, after officials found troubling antisemitic and racist statements written by their accused killer, according to Suffolk District Attorney Rachael Rollins.
Ramona Cooper, 60, a staff sergeant in the Air Force, and David Green, 68, the retired trooper, were each shot multiple times Saturday afternoon by 28-year-old Nathan Allen, after he crashed a stolen truck into a home on Shirley Street, Rollins said.
Cooper was shot three times in the back by Allen, who fired seven rounds into Green’s head, neck, and torso, according to Rollins.
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Allen died Saturday after exchanging gunfire with a Winthrop police sergeant who had responded to the chaotic scene, which unfolded in front of terrified residents, including children.
During a Sunday press conference at the scene, Rollins pledged to find out what triggered the deadly violence. She said investigators believe Allen acted alone.
“This is a sad day. 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,” Rollins said. “And we will find out why, and find out more about this man who did this.”

Officials are continuing their investigation into the incident, which unfolded along a short stretch of Shirley Street on what had been a quiet afternoon, Rollins said.
The truck, which Allen stole from a plumbing company, crashed into a home near the corner of Cross and Shirley streets shortly before 3 p.m. Saturday, according to police.
Allen fled the truck, jumped over a fence, and shot Cooper and Green a short distance from the wreck, according to officials. Fire Chief Paul Flanagan said Saturday that the crime scene covered about a quarter of a mile.
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During the subsequent police investigation, officials found “troubling white supremacist rhetoric” handwritten by Allen, Rollins said. The statements included antisemitic and racist statements against Black individuals, she said.
In a written statement Sunday night, Rollins said Allen, who drew swastikas, wrote about the “superiority of the white race” and of “whites being ‘apex predators’.”
In the statement, Rollins said Allen had a doctorate, was married, and employed. To all external sources he likely appeared unassuming, she said.
“There is a growing national, and global, problem with extremism and white supremacy. The FBI believes the most serious domestic violent extremist threat comes from ‘racially or ethnically motivated violent extremists, specifically those who advocated for the superiority of the white race,’ ” Rollins said.
During his rampage, Allen walked by several people who were not Black, and they were not harmed, Rollins said.
“They are alive, and these two visible people of color are not,” Rollins said, later adding, “It was a tragedy that it was two people; it could have been many, many more.”
Rollins, when asked if Green died a hero by entering the fray with Allen, responded, “Absolutely.”
“He was heroic, in the 36 years he gave to law enforcement, just as Ramona Cooper, serving our country in the Air Force, was a hero as well,” Rollins said. “It’s just a really tragic day in Winthrop.”
Cooper’s son, Gary Cooper Jr., said in a statement sent to WCVB-TV that she “was a good person, she would help anyone who needed it, she was caring and selfless. … We are heartbroken and she will be missed, just a senseless thing to have happened.”
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Rollins said authorities do not know where Allen was going Saturday, but the scene is close to Jewish houses of worship. He was traveling at twice the speed limit when he crashed, she said.
Rollins said Allen, who was legally licensed to carry a firearm, was not on her radar.
“He had nothing in his background check,” Rollins said.
Winthrop police Chief Terence Delehanty said at the press conference that there is no tolerance for hate in the community, and local officials are preparing to offer counseling during the coming week.
“This is obviously a tragic event, a traumatic event, and a lot of people don’t see those aftereffects for days or weeks to come,” Delehanty said.
He said the sergeant who was involved in the confrontation with Allen has been released from the hospital. Delehanty said the sergeant, who was not named, was “extremely heroic” during the incident.
The sergeant has been placed on administrative leave during the investigation according to procedure, a spokeswoman said.
“He isolated a significant threat to this community and ended that threat,” Delehanty said. “It’s something we don’t wake up in the morning wishing to do.”
Rollins praised the responding police sergeant for “saving many more lives in Winthrop.”
Earlier in the day, people gathered to commemorate Green and Cooper, some placing bouquets of flowers on fencing erected outside the wrecked building.
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No one answered the door Sunday afternoon at the three-story red house where Green lived. A knock on the door at Cooper’s apartment received no response Sunday.
“The families of two innocent bystanders today are mourning the killing of their loved ones by the assailant in Winthrop yesterday,” State Police Colonel Christopher Mason said in a statement mourning Green’s death.
Green served for 36 years in law enforcement, according to the statement. He began his career as a Metropolitan District Commission Police Officer in 1980 and became a trooper 12 years later when the agency merged into the State Police.

He retired in 2016, according to the statement.
“Trooper Green was widely respected and well-liked by his fellow Troopers, several of whom yesterday described him as a ‘true gentleman’ and always courteous to the public and meticulous in his duties. From what we learned yesterday, he was held in equally-high regard by his neighbors and friends in Winthrop,” Mason said in the statement.
“Trooper David Green more than upheld the ideals of integrity, professionalism, and service to others that are the hallmarks of a great Trooper. We are heartbroken by his loss and offer our condolences to his family and friends,” Mason said.
Among the mourners was Nick Tsiotos, 66, who also said Sunday he is heartbroken over the loss of his friend, Green, his high school classmate and basketball teammate, during the shootings Saturday.
“He was the best there was of humanity,” Tsiotos said during an interview across the street from the scene.
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Tsiotos called Green a “super human being.”
Green, a lifelong resident of Winthrop, spent four years in the Air Force.
“He was loved by all his classmates, all his neighbors,” Tsiotos said. “He had great character, he served with honor, he would help anybody, and that’s the kind of person he was, to go right into the terrible situation to try to save people.”
Tsiotos said he had coffee with Green the morning of his death. Later that afternoon, Green came to see Tsiotos and gave his wife some cherries. Green also offered advice to his college-aged son, who is “devastated,” Tsiotos said.
Tsiotos said the hours since the tragedy have felt like “a bad dream.”
At the trooper’s home near the site of the crash and shootings, mourners had placed five brightly colored bouquets around the front mat.
Green’s neighbor, Norma Leach, said she was sitting outside with him at the time of the shooting.
“He was a real nice guy, if you knew him, he’d be your best friend,” Leach said.
At the nearby alleyway where neighbors said the retired trooper was shot, mourners had placed bouquets and candles. Tsiotos said he suspects Green ran into the fray, confronted the shooter, and kept him from taking any more lives.
A neighbor on Saturday said he found a woman, later identified by officials as Cooper, in the street.
A woman who lives in the building where Allen lived and asked not to be named for privacy reasons, said that he seemed “so nice, but there was something a little off about him.”
She said he moved in to the building recently. When they met, he told her he was a physical therapist and offered to help her with her son, who is multiracial and has sensory processing disorder.
She said Allen often sat outside the building writing, as if he was “taking notes.”
“He had so many packages come, he always had packages coming,” she said in the lobby. She looked down, and saw that two of four packages on the ground were addressed to him.
Around 5:30 p.m. Sunday, police evacuated residents from the building as they investigated Allen’s packages in the lobby. People were allowed to return about 30 minutes later.
At Allen’s apartment, a woman answered a call from the building’s lobby, but quickly hung up.
Allen attended the University of Massachusetts Dartmouth, according to a Globe columnist’s story published last August that profiled Allen and his proposal to his then-fiancée amid the pandemic. The couple worked to include the woman’s grandfather in the ceremony and decided to hold the wedding at his nursing home.
Allen was on track to becoming a physical therapist and had just completed his schoolwork. He was expected to start an internship in Plymouth last year.
The truck involved in the Saturday crash was owned by Rapid Flow Inc. A man who answered a phone number listed for company owner Mark Meads declined to comment Sunday.
Police said two people pinned inside a car that crashed a short distance away from the destroyed building suffered non-life-threatening injuries.
Three people injured Saturday were treated in the Emergency Department of Massachusetts General Hospital, according to a spokeswoman. On Sunday, MGH spokeswoman Julie Cunningham said two of those patients had been discharged and a third remained at the hospital in fair condition.
It was not clear the nature of the third person’s injuries on Sunday.
Brian Marks, 39, the owner of the building destroyed in the crash, said in an interview at the site Sunday that his “heart goes out to those families” of the victims.
On Sunday, the ruined structure had become a makeshift shrine; mourners left flowers on the fencing erected around the site. One person left a personal message to the victims.
“Praying you are dancing in the sunshine and singing with the angels,” the note said. “R.I.P.”
Mike Bello and Laura Crimaldi of the Globe staff and Globe columnist Thomas Farragher and correspondent Jack Lyons contributed to this report.
John Hilliard can be reached at john.hilliard@globe.com. Camille Caldera was a Globe intern in 2022.Follow her on Twitter @camille_caldera.