GROTON — Wagner Alcocer and his wife were scrolling through real estate listings on their computer Friday evening when they heard a voice asking for help outside their home on Common Street.

When Alcocer, 52, looked up, he saw a naked young man covered head to toe in mud standing inside their screened-in back porch. He had blood on his face. He was calm. He looked right at Alcocer.

“Help me please, help me please,’’ the young man said. “I murdered four people.’’

A block away on this road lined with stately homes and rolling lawns, police later found the bodies of four people who had been bludgeoned to death. But at 5:45 p.m. on Friday, Alcocer looked at the young man’s bright red eyes and blank face, and decided it couldn’t be true. There was simply no way he had killed anyone, Alcocer thought.

“Those words, you don’t expect,’’ he said in an interview Saturday.

He offered the man a chair to sit in the yard. Also, a drink of water. Then he called police.

Alcocer’s account of the disturbing visit provided the first glimpse into the grisly killings at 80 Common St. Middlesex District Attorney Marian T. Ryan described the murders Friday night as “a tragic incident of family violence,’’ but declined Saturday to provide details or name the victims.

Orion Krause, 22, is being charged with four counts of murder, Ryan said at a news conference late Friday night. An e-mail from officials at Oberlin College & Conservatory in Ohio identified Krause as a 2017 graduate of the liberal arts school famed for its music program.

“The nature of this crime is horrific, and the grief of family and friends immeasurable. And yet Orion is one of our own,’’ said the e-mail signed by Oberlin’s president, Carmen Ambar, and Andrea Kayln, dean of the conservatory.

Relatives of Krause reached Saturday by the Globe declined to comment.

Krause and the victims knew each other, according to authorities, who said the public is not in danger. Ryan has said the dead were an elderly man and woman and two middle-aged women, but she declined Saturday to describe their relationship to Krause.

Three victims were found inside the home and a fourth was found outside, according to authorities.

Relatives said Bertha Mae Parker, 68, a caretaker for an elderly couple who lived in the home, was among those killed.

“I can’t fathom why somebody would do this,’’ said Mary Webb, Parker’s sister. “It’s still such a shock.’’

Parker hailed from Louisiana, where she was raised in a family of 11 children, said Bit Owens, another sister. A cook also worked in the home where Parker died, Webb said.

She recalled how Parker visited her last month in Bellows Falls, Vt. The sisters ate at a steak house and shopped at Market Basket and Jo-Ann Fabrics, Webb said.

Parker was a doting mother who was devoted to her faith, she said.

“I know that my sister enjoyed her work. She was always thinking highly of these people,’’ Webb said. “For this kind of thing to happen, it’s so senseless.’’

Alcocer said he didn’t learn of the killings until after medical personnel took the man away from his house.

When he saw him on his porch, Alcocer said, he was concerned that the young man would run away, so he told him to go sit in a chair in the backyard. The man agreed, Alcocer said, but only if Alcocer would open the door to the outside for him. Alcocer told his wife, Thekla, 51, to stay back.

“I need my sleeping pills,’’ the man said, as Alcocer walked him outside to sit down.

Alcocer offered the man water, and he refused. He asked the young man where his clothes were. “I left them in the woods,’’ the man replied, according to Alcocer.

Alcocer walked back inside to call 911. Behind him, the man sat rigidly in the chair. He had blood on his knee and back as well as his face, but beyond a few scratches, Alcocer saw no injuries. He was just a youngster, Alcocer remembered thinking. He needed help.

When police arrived, the Alcocers gave them a white sheet to give to the man to cover himself. They listened as the two officers asked the young man where he’d come from and how he’d gotten there, then read him his Miranda rights before handcuffing him and walking him down the driveway.

A little less than an hour later, a detective came to the Alcocers’ door with shocking news.

“It looks like what he said is true,’’ the detective said.

When the detective told him what happened, Alcocer immediately thought of the elderly couple who used to walk up and down the street in the afternoon holding hands. The man wore a wide-brimmed hat, he said, and they always waved. Sometimes they had a caretaker with them.

On Friday, Alcocer and his wife had taken their own walk, down past the couple’s home and back, just 10 minutes before the young man arrived at their door. They hadn’t heard a thing.

“At first I couldn’t believe — four? Four?’’ Alcocer said on Saturday.

Jack Feeney, who also lives on Common Street, said the couple who lived at the site of the slayings were in their 80s.

Joshua Degen, chairman of Groton’s Board of Selectmen, said residents are stunned.

“As much due diligence as a public safety office can do, they can’t predict a deranged individual intent on wreaking havoc and creating turmoil up to and including these deaths,’’ he said.

Alcocer said he was haunted by the encounter.

“It was very, very hard to sleep,’’ he said. “I have in my head this image of this kid looking at me and saying, ‘I murdered four people.’ ’’

Martha Schick and Aimee Ortiz contributed to this article Evan Allen can be reached at evan. allen@globe.com. Follow her on Twitter @evanmallen. Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi.