Mass murderer Connor Betts once choked a friend when she tried to stop him from “being mean” to his sister, the woman said in a new interview.

Taylor Gould, now 22, told the Cincinnati Enquirer she once went over to the Betts home for a sleepover with his sister, Megan, a close friend of hers.

Gould said she was bothered by the way Connor treated his sister — who was among the nine people gunned down this weekend in Dayton’s Oregon District entertainment area.

“He was being really mean to her,” Gould told the outlet, so she decided to step in.

“He strangled me because I got in his face to leave [Megan] alone,” she said.

He held onto her until Connor’s tearful mother begged him to stop, she told the paper.

Gould said that since then, she had never spoken to anyone about the incident, and her relationship with the family was severed.

“His mom saw it,” Gould added. “They were [going to] talk to someone.”

Thinking back on the incident, Gould said she considers Connor “a psychopath the school ignored.”

Her statements echo those of Connor’s ex-girlfriend Caitlyn “Adelia” Johnson, who called Connor “the product of a failed system.”

“A system that stigmatized mental health and recovery,” she wrote of her former flame in a Medium post published Tuesday. “A system that makes the mentally ill feel broken and unworthy of help. He didn’t want to seek help because of the stigma, he just wanted to be better and he didn’t know how.”

Another ex-girlfriend, Lyndsi Doll, said that Connor was in desperate need of professional help, and talked often about “dark, evil” things he was hearing in his head.