A Ronkonkoma man charged with strangling a married friend and setting her house on fire told detectives his victim died during "rough consensual sex," a Suffolk prosecutor said Thursday.

Christopher Bayer, 22, was among a group of friends who had gathered at Laura Giampino's Ronkonkoma house Sunday and was questioned by police after the discovery of her body the following morning, authorities said.

Speaking at Bayer's arraignment in a Suffolk courtroom Thursday, Assistant District Attorney Diane Merrifield said Bayer told police he had sex with Giampino, 20, on Memorial Day.

Bayer confessed how he used a piece of clothing, identified in court documents as a sock, to bind Giampino's mouth and neck during sex, and that she collapsed on the floor, Merrifield said.

"He subsequently realized that she was dead and tried to set the house on fire to cover up the crime," Merrifield said.

Bayer, who was arrested Wednesday, hung his head as he pleaded not guilty to second-degree manslaughter in First District Court in Central Islip. He was held without bail.

Giampino was found dead by firefighters in her Hawkins Avenue home. Officials said her body had been badly burned, making the cause of death initially difficult to determine.

Suffolk Det. Lt. Jack Fitzpatrick said police had interviewed several of Giampino's friends, including Bayer, who they said left the house about 5 a.m. Sunday. Police said Bayer returned later and had sex with Giampino.

The criminal complaint filed Thursday quotes Bayer describing Giampino's death. "I was holding the clothing with both hands and Laura moved the clothing down around her neck ... I saw blood on her mouth, then checked her pulse and realized she was dead," the document states.

Caryn Pesce, Laura Giampino's mother, said she doubted Bayer's explanation. "My daughter would not be having sex with this man. ... She was murdered in cold blood."

The parents of Laura Giampino's husband, Michael Giampino, identified Bayer as the boyfriend of the victim's best friend. Fitzpatrick said a grand jury will review the case and that he expected other charges. Police declined to discuss how they believe the fire was started.

Michael Giampino's father, Richard Giampino, 51, of Centereach, said his son was stunned and despondent. "He feels responsible, like if he had been home none of this would have happened," he said.

Michael Giampino, 24, who married Laura in Las Vegas in December, entered the Suffolk County jail on May 11 to start a 45-day sentence after pleading guilty to a charge of menacing. According to court documents, he threatened two minors with a pocketknife outside a Brookhaven library in February. "He's thinking he's lost everything, that he can't go on," his father said.