CONCORD, N.H. — The warnings came through the wall vents at King Cottage: Beatings had begun.

Michael Gilpatrick, who spent three years at New Hampshire’s youth detention center in the late 1990s, said he and other boys sometimes stood on their toilets, yelling into vents to spread word of approaching staff.

“Once they went into the first room, and restrained the first person and beat him, they’d go right down the line and do it to every single one of us,” he said. “You can hear it happen. You can’t necessarily see it, because you’re locked in yourself. And who knows what else they were doing in there, because a lot of us kept that stuff to ourselves.”

Gilpatrick, 38, isn’t keeping much to himself these days. He filed a lawsuit Monday alleging he was physically and sexually abused at the former Youth Development Center in Manchester, which has been the target of a criminal investigation since 2019 and is slated to close in 2023.

It’s the second of what could be hundreds of individual lawsuits after a judge dismissed a class action suit in May, leaving only the lead plaintiff’s claims intact. More than 300 men and women have come forward with allegations involving 150 staffers from 1963 to 2018 at what is now called the Sununu Youth Services Center.

Gilpatrick is suing the state, the youth center and five of the 11 men who were arrested in April and charged with either sexually assaulting or acting as accomplices to the assaults of more than a dozen teenagers.

Among them, Bradley Asbury and James Woodlock are accused of restraining Gilpatrick while he was assaulted by Jeffrey Buskey and Stephen Murphy in 1997 or 1998. A state trooper testifying at Asbury’s probable cause hearing said colleagues described the four as a clique or “the muscle” of the cottage, and said they often used physical force to deescalate conflict.

Gilpatrick wouldn’t discuss that episode in an interview with The Associated Press, but he said the teens referred to the four as a “hit squad” because they responded to every incident, even minor arguments between youths, with violence.

“I’ve seen them personally respond to hundreds of incidents, where they could have defused the situation in a lot better way, than bringing the kid down to the ground with a knee on the back of the neck, dropping elbows and kicking them, and dragging them back to the cottage,” he said.

The lawsuit also names the state health and human services commissioner and several former staffers, including one who has died. Woodlock’s attorney declined to comment Monday because he had not yet received the lawsuit. Attorneys for the other defendants did not immediately respond to calls and emails Monday, nor did a spokesperson for the Department of Health and Human Services.

In addition to physical and sexual abuse, Gilpatrick alleges, he was held in solitary confinement for as long as three months at a time.

“And then it would just become a daily occurrence where they would come in to antagonize us … start throwing our stuff around, take our pictures off the wall, rip them up, whatever,” he said. “Just a way to get under our skin so we could get at them. And it just gives them another reason to keep us in our room even longer.”

Staffers sometimes removed everything from the room, even the mattress, and left him there in his underwear, he said. He didn’t report the abuse, he said, because in some cases, supervisors were the abusers.

“There was nobody you could go to at YDC to talk to. You were literally stuck in your own thoughts, in your own fear every single day,” he said. “That place turned us into what we were. I can’t say what I am now because I’m a better person now. But coming out of that place, I was a monster.”

The lawsuit also alleges that abuse was pervasive and widely known by supervisors, and that abusers threatened physical retaliation if victims reported them. Gilpatrick’s attorney, Rus Rilee, said Monday he represents 375 clients with similar claims.

“Today is only the beginning of hundreds of lawsuits that will be filed over the coming weeks against the state on behalf of the brave survivors of decades of systemic governmental child abuse,” he said.

Gilpatrick left the youth center just before he turned 17 and was in prison within two years. He spent more than a dozen years behind bars and frequently used drugs, but now says he hasn’t used for four years and co-owns a waterproofing business.

He has two children with his wife of 16 years and praises her for standing by him. One of the many tattoos covering his arms, legs and torso features angels battling demons.

“That’s the biggest thing I struggle with,” he said. “Trying to keep myself good, but fighting with everything that I’ve dealt with that brought me down all these years.”