On Thanksgiving Day in 1995, the Fairfax County, Virginia area awakened to news of an early-morning house fire, with a female body found in the house. It seemed like a horrific tragedy. But what everyone thought was a terrifying accident was soon found to be much more nefarious.

Fire investigators looking into the cause of the blaze found smatterings of blood, a knife, and a bloodied rolling pin, according to Oxygen’s Homicide for the Holidays. It soon became clear to them that there was likely something more sinister at play.

The body was identified as 20-year-old Anne Harper, home from college for Thanksgiving. The house was her mother’s, Elizabeth, and her brother Matt and her grandmother, Elizabeth’s mother, were also staying at the home.

“I didn’t note anyone breaking or entering in the structure, so now we’re not looking for the Boogeyman, we’re looking for somebody in the world of this family,”  Jeff Miller, a now-retired detective with the Fairfax County Police Department, told Homicide for the Holidays.

But it was still unclear who that person was, or why they would harm Anne.

What happened to Anne Harper on Thanksgiving morning?

Matt Harper spoke with police, saying he, his family, and some friends had gone out to eat dinner that night in preparation for spending the next day cooking. Afterward, he and Anne had gone to see a movie with some friends. He later dropped Anne off at their mother’s house and went to spend the night at his girlfriend’s house.

Around 2:00 a.m., the newsroom scanner picked up an emergency call for a house fire, according to Gail Pennybacker, a now-retired journalist for WJLA, the Arlington, Virginia area ABC affiliate who was working that night.

The fire was at the Harper house.

When emergency personnel showed up to the residence, they found Anne Harper’s body.

How did Anne Harper die?

The local medical examiner performed an autopsy on Anne’s body and ruled that the cause of her death was not, as might have been expected, smoke inhalation due to the fire, but stab wounds to the body. The autopsy also found that she suffered blunt-force head trauma.

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Investigators developed a theory that the fire was set not to intentionally kill Anne, but to cover up the evidence of what happened, Miller explained.

They also believed that the fire was set to potentially kill Elizabeth because they had found what appeared to be gasoline or an “ignitable liquid,” as now-retired fire investigator Terry Hall termed it, trailing from the stairs to Elizabeth’s bedroom, as well as within the bedroom itself.

Initially, investigators were a bit stumped by who would do such a thing. Then, Anne’s father told investigators that Anne had met up with an old ex-boyfriend when she arrived back in town. Eventually, investigators tracked down Anne’s ex in Houston, where he was spending the holiday and, with the help of the Houston Police Department, questioned him about his get-together with Anne.

Investigators were able to clear Anne’s ex as a suspect in the case. However, without any other leads, it eventually went cold.

But while doing a periodic review of still-open cases, Miller returned to Anne’s case file and recalled that Matt Harper wasn’t wearing shoes when he arrived at the hospital to see his mother the night of the fire. Given that it was late November, that struck investigators as odd.

He also had a stain on his jeans that looked like it could be blood. Investigators asked Matt about the stain, and he explained that he and his girlfriend had cooked pasta previously.

Miller later theorized that perhaps Matt had been at the house that night and then ditched his shoes in the creek behind the Harper home to get rid of any potential evidence that would have been on them.

As investigators continued to work the case, they became more convinced that the culprit could have been Matt, and soon had enough evidence to make an arrest.

Who killed Anne Harper?

Almost three years after Anne was found dead in her mother’s home, investigators traveled to James Madison University and pulled Matt Harper out of his college lecture in order to arrest him for the death of his sister, Anne, as well as arson.

After Matt’s arrest, Elizabeth continued to insist upon his innocence.

But in a surprise twist, Matt pleaded guilty to murdering his sister and, in 1999, was sentenced to 35 years in prison.