WOBURN — Inside the Groton home where Bertha Mae Parker worked as a caretaker, an elderly couple and their daughter had been bludgeoned with a baseball bat. From upstairs, the 68-year-old tried to escape.

But as Parker fled the Common Street residence on Sept. 8, she was chased down by Orion Krause, who had allegedly killed his mother and grandparents after dining with them in the kitchen, a prosecutor said Wednesday.

“She went out into the driveway trying to get away,’’ Middlesex Assistant District Attorney Thomas Brant said as Krause, 23, was arraigned on four counts of murder. “Orion Krause went out there with that same baseball bat, hitting her in the back of the head and ... knocking her to the ground.’’

Officers found an 8-foot trail of blood next to Parker’s body, which was left in a flower bed, Brant said.

Krause kept his composure as he pleaded not guilty but trembled when the clerk identified his 60-year-old mother, Elizabeth, as one of the four victims.

His father, Alexander, watched the proceedings from the gallery, accompanied by four other family members. He nodded to his son when he appeared in the prisoner’s dock and pressed his hands together as the indictment for his wife’s murder was read aloud.

Alexander Krause, who has attended other court hearings for his son, declined to speak with reporters after the arraignment, held in Middlesex Superior Court. Orion Krause’s lawyer, Edward Wayland, said he would likely pursue an insanity defense.

“I would say it was mental illness that caused this to happen and only mental illness,’’ he said.

Krause, a jazz drummer who grew up in Maine and graduated last year from Oberlin College and Conservatory in Ohio, is being held without bail at Bridgewater State Hospital, a psychiatric facility run by the state prison system. He has been found competent to stand trial.

Wayland declined to say what Krause is being treated for, saying he couldn’t recall the precise diagnosis made by doctors. Krause is due back in court next month.

Elizabeth Krause, of Rockport, Maine, and her parents F. Danby Lackey III, 89, and Elizabeth Lackey, 85; suffered massive head wounds in the attack, Brant said. The grandparents were sitting in reclining chairs they were mostly confined to because of their health, he said.

Their daughter was found in a chair near an island in the kitchen.

“The wounds I would describe mildly as horrific,’’ he said.

Before the attacks, Krause twice told a former professor at Oberlin that he intended to kill his mother, a threat Maine authorities relayed to Groton police on the day of the murders, the Globe has reported. However, Groton officers didn’t receive the information until after the slayings.

They were summoned to Common Street around 6 p.m. that day after a neighbor alerted police that Krause was at his home, naked and splattered with blood. Krause kept saying he had “murdered four people,’’ the neighbor told police.

The day before the killings, Orion Krause had driven away from his house in Rockport, Maine, without telling anyone. His departure made his mother worry that he might commit suicide.

The next morning, Orion Krause called his mother and said he was in the Boston area and needed a ride home, authorities say. Elizabeth Krause drove to Massachusetts to pick him up, and on the way back to Maine, they stopped at her parents’ house in Groton.

Orion Krause faces a maximum of four life sentences without the possibility of parole if convicted of first-degree murder for each death.

John R. Ellement of the Globe Staff contributed to this report. Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi.