A New Hampshire man faces up to 24 years in prison after pleading guilty to killing his father more than 20 years ago.

Douglas Herlihy, now 40, has admitted to killing his father as a 17-year-old, according to the New Hampshire Department of Justice.

The father and son had a turbulent relationship with prior violence and law enforcement involvement before the father’s death.

Paul Herlihy, 50, was found on August 27, 2003, during a welfare check requested by a relative.

Officers entered his Milford, New Hampshire home through a window. They immediately noticed "hundreds of flies and the strong odor of decomposition," court records show.

Paul Herlihy’s body was found on the kitchen floor wrapped in carpet and covered with a blue tarp. Officers found blood spatters on kitchen cabinets, the refrigerator, walls and the ceiling.

The autopsy determined the death to be a homicide caused by blunt-force trauma within the past four days.

The medical examiner found injuries to Paul Herlihy’s nose and jaw, fractures to his skull, and damage to his voice box. Investigators said the killer repeatedly struck him in the head, causing his death.

In the backyard of the home, directly outside Douglas Herlihy’s bedroom window, the police found carpet and carpet padding with blood stains. Investigators concluded that the carpets and padding were pushed out of Douglas Herlihy’s bedroom window, which was open when investigators visited. DNA testing suggested the blood on the carpet and padding could belong to Paul Herlihy.

Inside the younger Herlihy’s bedroom, a closet door was covered with a towel. When investigators removed the towel, they found "large handwriting on the door, which read: ‘I WILL SEE YOU IN HELL,’" according to an arrest affidavit.

A killer was never identified.

In the months and years after Paul Herlihy’s death, his son had repeated brushes with the law, including for drugs and a stolen vehicle. When speaking with police after an arrest in 2020, he told an officer that he knew the court would "throw out the charges."

"That's what I do. I beat cases. I beat my first body when I was 17!" he said, according to his arrest affidavit.

"I assumed he was implying that he had killed people in the past," the officer said.

But Douglas Herlihy consistently denied any involvement in the killing of his father to family, court records show.

When investigators approached him in 2010 about the investigation into his father’s killing, Douglas Herlihy referred them to his attorney.

Based on the investigation's findings, an arrest warrant for Douglas Herlihy was issued in June 2025. He was quickly arrested in Saugus, Massachusetts, and was later extradited to New Hampshire.

Douglas Herlihy was charged with two counts of second-degree murder and falsifying physical evidence.

He negotiated a plea agreement for 12 to 24 years in the New Hampshire State Prison on a manslaughter charge. The agreement also suspends for 20 years a potential sentence of 3 ½ to 7 years for attempting to falsify evidence.

"This case is a reminder that the pursuit of justice does not end with the passage of time," said New Hampshire Attorney General John M. Formella.

"The New Hampshire Cold Case Unit and our law enforcement partners remain committed to pursuing answers and accountability, even decades after a crime. That work takes persistence, patience and a determination to follow the evidence wherever it leads. I commend the investigators and prosecutors whose continued efforts brought this case to an important resolution."

A sentencing hearing will be scheduled for a date in early 2027.

The Herlihy family said they wanted to maintain their privacy and did not wish to speak with the media according to the New Hampshire Department of Justice Cold Case Unit.

Herlihy's attorney could not immediately be reached for comment.