A 21-year-old Selkirk man with a history of mental illness who was imprisoned for arson at age 17 and whose family said he had been repeatedly harassed by older inmates hanged himself in his cell Thursday at Fishkill state prison, state corrections officials said.

Benjamin Van Zandt was found dead in his cell by a prison staff member making rounds at 6 p.m., said Linda Foglia, a spokeswoman with the state Department of Corrections and Community Supervision.

Van Zandt had been placed in solitary confinement in a special housing unit, or SHU, on Oct. 28 for fighting with another inmate, Foglia said. Prisoners call it The Box. He died two days later.

Van Zandt, a Bethlehem High School student and Boy Scout who was close to achieving the rank of Eagle Scout when he was arrested, set fire to the home of a vacationing Delmar family to cover up the theft of credit cards. He pleaded guilty in Albany County Court in 2010 to third-degree arson, a Class C felony, and was sentenced to four to 12 years in prison.

He was the 11th suicide this year among New York's 54,000 state prisoners. He was also the youngest inmate to take his own life, Foglia said.

Foglia would not release details about Van Zandt's death and would not say whether Van Zandt was under a suicide watch or had received any psychological monitoring. She did say that there was no indication of foul play.

She said his death is under investigation by multiple agencies, including the State Police, the Dutchess County coroner and the state Commission of Correction, which investigates inmate deaths.

A preliminary report by the commission, which was notified of Van Zandt's death in a timely manner, has not been completed, spokesman Walter McClure said.

Van Zandt's mother said the family was trying to get information, even as they prepared for their son's funeral on Friday at the First Unitarian Universalist Society in Albany.

"We're in the process of grieving for our son," she said, and declined to discuss it further.

In an obituary the family published in the Times Union, Van Zandt was described as a "loving, caring person, with a wonderful sense of humor."

The family has retained attorney Cheryl Kates of Ontario County, who specializes in prisoner litigation.

"The family is very upset," Kates said. "I want to give the family time to grieve. I ask that people respect their privacy until after the funeral is over."

Friends of the family described a confluence of mental illness and intense harassment by inmates against Van Zandt. He entered the prison as a baby-faced teen who played violin in his school orchestra and excelled at math and science before he was placed among hardened criminals twice his age.

The fire he admitted setting at the 112 Hasgate Drive home did damage estimated at $455,000 after Van Zandt smashed a window, sprayed gasoline in several rooms and used a cigarette lighter to ignite the blaze.

He initially was sent to Woodbourne Correctional Facility in Sullivan County, where he took courses at Bard College and enjoyed his studies, according to a family friend who did not want to have his name used. Bringing back a piece of bread from the cafeteria to the dormitory at the request of another inmate got Van Zandt expelled from the Bard program and he became depressed, the friend said.

"He was moved to another unit and things went down from there," the family friend said. Older prisoners began to exploit, intimidate and harass him. His parents appealed to prison officials, who transferred Van Zandt to Mid-State Correctional Facility in Oneida County. Both are medium security prisons with dormitory housing.

At Mid-State, he was given an S designation, meaning he had a serious mental health diagnosis and was housed in a crisis unit with additional monitoring and treatment services, the family friend said.

Van Zandt was allowed to exercise and walk around in the general population two hours each day, but reputed gang members coerced him into carrying drugs, the family friend said. Van Zandt was caught, disciplined and transferred to Fishkill, also medium security.

"He was a very fragile young man and it's all terribly sad, but you could see this coming," said Robert Corliss of Schenectady, a retired advocate for the National Alliance on Mental Illness and Mental Health Association in New York State. He is a longtime advocate of prison reform for mentally ill inmates and worked with Van Zandt's family.

Corliss said Van Zandt's tender age was a factor in the harassment he suffered from other inmates. New York is one of only two states that puts prisoners as young as 16 in with adults.

"Ben ended up in a situation where he was continuously harassed and abused physically and mentally," said Corliss. "He had a nice, supportive family and they did everything they could to help him. I question whether he should have been placed in the SHU at all, given his serious mental illness."

Corliss helped win a legal settlement this year that limited the state's use of solitary confinement with inmates who are pregnant, younger than 18 or developmentally disabled. He and other advocates continued to fight for additional reforms, especially on behalf of mentally ill inmates in a decades-long legal battle to end what many experts deem "cruel and unusual punishment." The advocates also pushed for more mental health treatment services in prisons.

In 2013, there were 8,197 mentally ill inmates in a prison population of about 54,500 prisoners, according to state records. A 2012 New York Civil Liberties Union report, "Boxed In," documented roughly 4,000 prisoners who were locked down for 23 hours a day for violating prison rules. The average time in isolation was 150 days. The report found psychological damage and a rise in suicide attempts from punitive segregation in SHUs.

Dr. Stuart Grassian, a Boston psychiatrist, coined the term "SHU syndrome," in which prisoners confined for long periods in solitary show a range of symptoms of mental illness, including depression, increased paranoia, agitation, manic activity, delusions and suicide.

The Van Zandt family friend said the mother had visited her son recently and discovered that prison officials had taken away his antidepressant medication for an unknown reason. It was unclear if he had resumed the medication at the time of his death, the family friend said.

Van Zandt had served more than 3½ years of his sentence, was due for a parole hearing in December and was eligible for parole in January, according to prison records.

"It's so tragic," said Alison Coleman, director of Prisoners Families of New York, who worked with the Van Zandt family. "I will wait for the investigation and report, but it seems like his case was not handled well."

"We've got a long way to go on prison mental health issues," Corliss said. "We've been fighting a long time, but it's only been incremental progress."

pgrondahl@timesunion.com • 518-454-5623 • @PaulGrondahl