A man convicted of murdering a stranger in the 1970s has died at a Maine prison.

Albert Paul, 87, died about 3 a.m. Monday at Mountain View Correctional Center in Charleston, according to the Maine Department of Corrections.

His cause of death wasn’t disclosed, but corrections officials said it didn’t involve the coronavirus.

The Maine attorney general’s office and Maine medical examiner’s office have been notified of Paul’s death, as is standard procedure.

In 1972, Paul was convicted in a jury-waived trial of the murder of Ellen Donahue, who was found beaten and strangled in her South Portland home in 1971, and sentenced to life in prison.

Paul spent most of life since he turned 18 years old in prison, and was the oldest and longest serving inmate within the Maine prison system, according to the Portland Press Herald. Since the 1950s, the Maine Department of Corrections had spent more than $1.5 million to incarcerate Paul, the newspaper reported.