A San Francisco Bay Area serial killer died from natural causes after spending the last four decades of his life on San Quentin prison’s death row, state officials said.

Anthony J. Sully was sentenced to death on June 3, 1986, for murdering six victims. Sully was a former Millbrae, California police officer who beat, raped, and killed prostitutes.

“Anthony J. Sully, housed at San Quentin Rehabilitation Center on condemned status, died of natural causes Sept. 8,” California Department of Corrections and Rehabilitation officials wrote.

Sully, 79, was pronounced deceased at 2:21 a.m. Friday at an outside medical facility. A Marin County Sheriff’s coroner will conduct an autopsy.

The policeman-turned-serial killer had been locked in San Quentin since June 15, 1986. Sully was convicted by a San Mateo County jury of murdering Kathryn Barrett, 24; Barbara Searcy, 22; Gloria Jean Fravel, 24, Brendan Oakden, 19; Michael Thomas 24, and Phyllis Melendez, 20.

After leaving the police force in Millbrae, Sully set up an electrical contracting business at a warehouse in Burlingame. Inside the warehouse, Sully tied up, beat, and brutally raped prostitutes, according to court records filed in 1991 in response to one of his appeals. Some of the women were killed during the beatings.

Ronald L. Sanders’ photo was provided by CDCR.

A witness said Sully told her that the only difference between “killing someone now, and killing someone as a policeman,” was that police had permission to do it, court records state.

He murdered five women and one man “in bizarre episodes. He freebased cocaine and had sex with prostitutes at the warehouse, subjecting the prostitutes to rape, beatings, and other forms of violence. Although he denied committing any of the murders, extensive circumstantial and physical evidence, as well as accomplice testimony, supported his conviction on each count,” court records state.

A second former San Quentin prison death row inmate, 71-year-old Ronald L. Sanders, died on Tuesday from natural causes, CDCR officials said. Sanders was pronounced deceased at 10:02 a.m. at California Medical Facility in Vacaville.

Sanders was sentenced to death in Kern County on March 3, 1982 for the murder of Janice Dishroon Allen, 29. He was admitted to San Quentin’s death row on June 13, 1984.

There are currently 654 condemned inmates in CDCR prisons. California has not carried out a death row execution in 17 years. The last execution was that of Clarence Ray Allen held on Jan. 17, 2006, prison officials said. In 2019, Governor Gavin Newsom signed Executive Order N-09-19, instituting a moratorium on the death penalty in California.

San Quentin State Prison was once home to America’s largest death row. Earlier this year, Governor Newsom announced plans to transform and renamed the notorious lockup to “San Quentin Rehabilitation Center.”