ROCKPORT — A friend of the family of a Rockport man charged with four counts of murder in Massachusetts said Sunday that the victims are the suspect’s mother, her parents and their caretaker.

Orion Krause, 22, was arrested and charged Saturday after the slayings in Groton on Friday.

Orion Krause in his 2013 graduation photo from Camden Hills Regional High School.

Officials in Massachusetts have not publicly identified the victims. But Krause family friend Sherman Stanley of Monhegan Island said Sunday that the suspect’s mother, Elizabeth “Buffy” Krause, her parents and a caretaker of the elderly couple were killed.

Stanley is a friend of Orion Krause’s father, Alexander Krause. His identifications were consistent with those provided earlier Sunday by a Maine law enforcement officer who spoke on the condition of anonymity because he was not authorized to release the information.

Orion Krause is scheduled to be arraigned Monday morning in Ayer District Court in Massachusetts on four counts of murder, said Meghan Kelly, spokeswoman for the Middlesex District Attorney’s Office. She said the victims’ names are being withheld pending positive identification by the Office of the Medical Examiner and notification of family members.

Middlesex District Attorney Marian Ryan and Groton Chief of Police Donald Palma Jr. issued a statement after Krause was arrested Saturday, stating that all parties were known to each other and that this was “a tragic incident of family violence.”

The preliminary investigation suggests all the victims died of blunt-force trauma.

Orion Krause’s arrest on murder charges was met with shock and disbelief by those who knew him when he attended Camden Hills Regional High School.

“I was absolutely stunned,” Duryea Decker Griffith of Lincolnville said Sunday. “He was a really good guy. He was musically talented, smart, laid-back, I would say cool.”

Decker Griffith said he briefly saw his former high school classmate and band mate in Rockport on Wednesday, when Krause was with his family.

Camden Hills band director Nancy Rowe said Krause was a fabulous musician and a very nice, polite young man.

Orion Krause performs on the drums. He joined the Camden Hills Jazz and Concert Band in his sophomore year, and received the maestro award at Camden Hills in 2013 for a drum solo.

“He was topnotch in every way,” Rowe said. “I’m stunned. This is unimaginable to me.”

She said her heart goes out to his entire family.

Krause grew up in Rockport and was active in the Camden-Rockport schools from an early age. He was part of a group of fourth-grade students at the former Rockport Elementary School in 2005 who raised money to help victims of the catastrophic tsunami in Southeast Asia.

Krause played basketball and ran cross-country and track while attending Camden-Rockport Middle School, where he started to become known for his musical talent.

When Camden Hills Regional High in Rockport named him the visual and performing arts student of the month in November 2012, the school reported that Krause began playing music in fifth grade when he studied the clarinet. He switched to percussion in eighth grade, primarily because of the influence of some of his favorite musicians and the video game Rock Band, the school said.

That year, Krause received his first drum set for Christmas. He joined the Camden Hills Jazz and Concert Band in his sophomore year, and received the maestro award at Camden Hills in 2013 for a drum solo.

Some of his favorite artists at that time included King Crimson, Yes, Led Zeppelin, Genesis, David Bromberg and the Dave Brubeck Quartet.

After graduating from Camden Hills in 2013, Krause continued his music studies, attending Oberlin Conservatory within Oberlin College in Oberlin, Ohio, near Cleveland. The college’s website describes Oberlin as “a place of intense energy and creativity, built on a foundation of academic, artistic and musical excellence.”

Onlookers gather at the scene as police officers put Orion Krause, covered in a white sheet, into a police vehicle in Groton, Mass., on Friday.

Krause held a jazz drum senior recital at Oberlin in April, according to Oberlin’s website. He graduated from Oberlin in May, said Scott Wargo, director of media relations for the college. Wargo said the school could not provide any other information on Krause.

Outside of college in 2014, Krause was the drummer for the band Mostly Brothers & Company.

Groton is a town of roughly 10,000 people about 43 miles northwest of Boston. Shortly before 6 p.m. Friday, Groton police responded to a report of a person in need of assistance on Common Street. Upon arrival, investigators gathered information that led them to a second residence at 80 Common St. There they located the four victims: an elderly male and female and two middle-aged women. Three bodies were found inside the house and one was found outside.

The home where police say the killings occurred has been owned since 1992 by Danby F. Lackey III and Elizabeth C. Lackey, according to the town’s assessment records.

Neighbor Wagner Alcocer, 52, unwittingly became a witness when the suspect showed up at his back door, naked and muddy, Friday evening and calmly told Alcocer he “just murdered four people,” according to Alcocer.

Alcocer told the Associated Press that the suspect’s eyes were “very red” and he had cuts on his body and blood above his eye and knee, but he was unarmed and seemed vulnerable.

“He looked like a nice kid who needed help, he was skinny (and) tall,” Alcocer said. “I thought he was the victim of a prank, or in an accident or had a mental health problem. He wasn’t bleeding profusely or anything.”

Alcocer, who had never seen Krause until that night, had thought the alleged confession was “just crazy talk.” It wasn’t until Krause was later taken away in an ambulance that a detective confirmed to Alcocer that the killings had taken place, Alcocer said.

Krause has no criminal record in Maine, and local police reported no interaction with him.