A 60-year-old prisoner died by suicide at the Massachusetts Correctional Institution in Norfolk on Nov. 17, the state Department of Correction confirmed Tuesday.

The prisoner, Jorge Zerquera, was found at about 10:30 p.m. and sent by ambulance to a local hospital, where he died about an hour later, state prison officials said. His was the third suicide death in the state’s largest medium security prison since 2013, state officials say.

Advocates and people behind bars have expressed concerns about how Zerquera was treated in the days preceding his death. His suicide has also prompted broader concerns about highly structured units meant for prisoners with behavioral or other issues at Massachusetts state prisons.

Claire Masinton, a staff attorney at the state-funded Mental Health Legal Advisors Committee, said she heard from several prisoners at Norfolk who were “distraught and angry” about Zerquera’s death. He allegedly died in the prison’s Behavioral Assessment Unit, according to prisoners who reached out to Masinton. The unit is meant to house prisoners considered by the state to be an “unacceptable risk to safety,” where they can be confined for up to 21 hours a day.

“The real takeaway on the inside — and I think from a lot of folks on the outside — is this is all just solitary by a different name,” Masinton said.

Masinton on Monday received a letter from a concerned prisoner saying that Zerquera had been placed in the unit after an altercation with prison staff. He said correctional officers had “shaken down” his cell and withheld his medicine. He died hours later, according to the letter and other info she received from prisoners.

Bonnie Tenneriello, an attorney at Prisoners' Legal Services of Massachusetts, said she couldn’t confirm specifics of Zerquera’s death. However, she said conflicts with correctional officers often lead to people being sent to those units.

“What we have heard illustrates some of these systemic problems,” she said. “[Prisoners] live at the mercy and the discretion of the correctional staff.”

Also on Tuesday, officials from the Prisoners Legal Services called for a state investigation into the Secure Adjustment Unit at the state’s maximum security prison in Lancaster. In a press release, the nonprofit said they join a group of lawmakers and civil rights advocacy agencies seeking an investigation by Attorney General Andrea Campbell into the structured unit following a hunger strike by prisoners.

Behavioral Assessment Units are meant for prisoners who pose a risk to their own or other people’s safety, according to a state policy document. Secure Adjustment Units are housing units for prisoners that need structured programming and cognitive behavioral treatment, state documents show.

Department of Correction officials couldn’t immediately be reached for comment about the latest letter from Prisoner’s Legal Services. However, in the past, the state prison officials have defended the speciality units and denied they could be likened to solitary confinement.

State prison officials also said Tuesday that they couldn’t comment on specifics of Zerquera's medical history or about personnel matters. However, they said no correctional officers have had a “change in duty status” because of what happened in Norfolk. They said all unexpected deaths in state prisons prompt an internal investigation and a notice to the district attorney’s office.

Zerquera, the youngest son of Cuban immigrants, born in Chelsea, was nearing the end of his sentence and planned to move in with his sister upon his release, according to articles he wrote on Between the Bars, a blog for those in prison. State officials say he was an out-of-state transfer from Florida serving a first degree murder conviction.

Prison advocates say Zerquera was a well-liked prisoner and his death has taken everybody by surprise. Another prisoner wrote Masinton saying people at Norfolk were seeking answers about what happened.

“I think this tragedy points to some of the desperation that people feel within this system,” Tenneriello said. “Zerquera was really beloved.”