GEORGETOWN — A Georgetown man who murdered his mother with an ax almost 40 years ago will remain in prison after the Parole Board last month denied his sixth request to be released.

According to the Parole Board’s June 10 decision, Peter Holbrook struck his mother Alberta Holbrook several times on the head with a small ax while she was watching television in their home on June 25, 1980.

Holbrook’s mother was a 65-year-old retired widow at the time of the attack and her son was unmarried and unemployed. They lived at 11 Maple Street.

According to state documents, Alberta Holbrook was unconscious and bleeding from several cuts to the top of her head when police arrived that evening and her son told investigators he had been thinking about killing her for more than a year.

“She would lecture me,” Holbrook told investigators.

“I reached the bottom of the pit. I was hopeless. I couldn’t think of a way out of it. I was thinking of doing it from behind her. I shouldn’t have done it as I did it. It was just a game, really.”

Holbrook was charged with assault with intent to murder and assault and battery with a dangerous weapon to which he pleaded not guilty. His mother died three days later and her son would later admit to police that he committed the crime.

Holbrook was found competent to stand trial and criminally responsible. He pleaded guilty to second-degree murder on Feb. 21, 1981, and was sentenced to life in prison with the possibility of parole.

Parole Board records show Holbrook had a well-documented history of mental illness with his first known hospitalizations following multiple suicide attempts in the 1970s.

He also was hospitalized at Danvers State Hospital after violating probation on a breaking-and-entering charge in 1973.

Holbrook, who is now 67 years old, is imprisoned at Gardner’s North Central Correctional Institution.

He has been diagnosed with paranoid schizophrenia and has a history of noncompliance and trouble accepting that he suffers from a major mental illness, the Parole Board said in its ruling.

Holbrook appeared before the board for his sixth parole hearing on Aug. 20, 2018, and was reported to have incurred approximately 60 disciplinary reports by a May 7, 2013, parole hearing. His most recent disciplinary infraction came on July 18, 2018, when he assaulted another inmate, the ruling said.

The Parole Board again denied Holbrook’s request for parole on June 10 after he told them he killed his mother because he believed she was having an affair with a friend of his.

“He continues to demonstrate violent behavior towards others that may or may not be related to mental illness,” the Parole Board decision reads.

Holbrook’s next appearance before the Parole Board is scheduled for August 2021.