LOWELL, Mass. (AP) A Maine man who used a baseball bat to beat his mother, his grandparents and his grandparents’ caretaker to death in Massachusetts in 2017 has pleaded guilty.

Orion Krause, 26, of Rockport, Maine, was sentenced Wednesday in Lowell Superior Court to life in prison with the possibility of parole after 25 years after pleading guilty to four counts of second-degree murder, according to the office of Middlesex District Attorney Marian Ryan.

Krause had originally faced four counts of first-degree murder but admitted to the lesser charges under a plea deal with prosecutors.

The deal took into account Krause’s lack of criminal record, his relative youth and his mental health condition at the time of the killings, prosecutors said.

“The resolution of this case today in no way can erase the incalculable loss felt by the family and friends of these victims,” Ryan said in a statement.

Krause, who had recently graduated from Oberlin College, apologized in court and told the judge he was in a “psychotic state” at the time.

The victims killed in the Groton home on the evening of Sept. 8, 2017 were identified as Krause’s mother, Elizabeth Krause, 60; his grandparents Elizabeth Lackey, 85, and Frank Lackey, 89; and Bertha Mae Parker, 68, of Tewksbury, a home health care worker caring for the Lackeys.

The cause of the death of all four was determined to be blunt force trauma, with injuries to the brain and skull, prosecutors said.

Krause, who was 22 at the time of the slayings, was naked and covered in mud and cuts when officers found him at a neighbor’s house, according to the documents. He told officers: “I murdered four people.” After police wrapped him in a sheet, he began to sing quietly, according to the records.

Krause contacted one of his former professors shortly before the killings and told him of his intentions to kill his mother. The professor called police.