An Indiana woman who was once the nation’s youngest person on death row but whose sentence was eventually commuted to a prison term was found dead in Indianapolis on Tuesday.

Indianapolis police said 45-year-old Paula Cooper was found dead of an apparently self-inflicted gunshot wound outside a residence on the city’s north-west side. Cooper had been released from prison about two years ago, after the Indiana supreme court set aside her death sentence and gave her a 60-year prison term.

Cooper was 16 when she was sentenced to death in 1986 after confessing to her role in the murder of a 78-year-old Bible studies teacher the year before. Cooper admitted stabbing Ruth Pelke 33 times with a 12-inch butcher knife in a robbery that netted four youths $10 and an old car. Cooper was 15 at the time the crime was committed.

Her death sentence enraged human rights activists in the US and Europe and drew a plea for clemency from Pope John Paul II. In 1988, a priest delivered a petition to Indianapolis with more than 2 million signatures protesting Cooper’s sentence.

Pelke’s grandson, Bill Pelke, who organized opposition to the death penalty after his grandmother’s killing, said he was devastated to learn of Cooper’s death. He said he worked to help Cooper after realizing that’s what his grandmother would have wanted.

“My grandmother would have been appalled she was on death row and that there was so much hate and anger and desire for her to die. I was convinced my grandmother would have had love and compassion for Paula and her family,” he said in a telephone interview from Anchorage, Alaska, where he runs the Forgiveness Project, a charity that seeks to promote understanding and forgiveness.

Pelke said he visited with Cooper while she was in prison and had last spoke to her last August. He was expecting to hear from Cooper next month, when she was scheduled to be released from parole. He said she had expressed an interest in speaking for his organization.

“I have no idea what was going on in her life. I thought she was doing well from everything I had heard,” he said. “I had hoped she would travel with us. She had always told me she wanted to help young people to avoid the pitfalls that she had fallen into. She said she knew she had done something terrible to society and she wanted to give back.”

Two years after Cooper was sentenced to death, the US supreme court ruled in an unrelated case that those under 16 at the time of an offense couldn’t receive the death penalty. The court said such sentences were cruel and unusual punishment and thus unconstitutional.

Indiana lawmakers later passed a law raising the minimum age limit for execution from 10 years to 16, and in 1988, the state’s high court set aside Cooper’s death sentence and ordered her to serve 60 years in prison.

Cooper’s sentence was reduced due to her behavior in prison, where she earned a bachelor’s degree. She was released from prison on 17 June 2013 after spending 28 years behind bars.