A Grisly Double Murder Shocked Napa Valley. Three Cigarette Butts Led to the Killer's Capture

A grisly double murder in Napa Valley plagued the town's residents for a year — until three cigarette butts proved the smoking gun of the case.

PEOPLE reported on the murders shortly after they took place in October 2005 when, in the early morning hours after Halloween, an intruder broke into an unlocked window in Leslie Mazzara and Adriane Insogna's Napa Valley, Calif., house and slashed both women to death with a knife.

The murders were shocking, both because Napa Valley is a safe enclave known largely for its wine, and because the two women were so well-liked.

"The killings affected everyone," one local told PEOPLE. "It was like a Halloween movie come true."

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Mazzara, 26, was a former beauty queen who moved to Napa from South Carolina in 2004 to be close to her mother. She worked at a winery and "had such a bubbly personality," Renee Tollison, who knew Mazzara through the pageant circuit, told PEOPLE. "When she was happy, everybody around her was happy."

Mazzara moved in with Insogna, also 26, and another young woman that same year.

Insogna was athletic — an avid volleyball and softball player who worked as a civil engineer at the Napa Sanitation District. While there, she became close friends with a coworker, Lily Prudhomme, who was engaged to a man named Eric Copple. The friendship, cops said later, may have sealed her fate.

The case would take nearly a year to crack, with police interviewing 1,300 people and taking 218 DNA samples but making no arrests for months.

But there was a major clue: prior to murdering the women, the killer had smoked three cigarettes, dropping their butts outside.

Police had begun to narrow in on a suspect: Eric Copple, the beau of Insogna's work friend. He proved uncooperative when police tried to pin him down for an interview, but police felt sure the crime itself hadn't been entirely random.

On Sept. 22, 2006, police made an announcement: the killer had smoked Camel Turkish Gold cigarettes.

Days later, on Sept. 27, 2006, Copple was arrested. Fearing capture following the announcement of his favored brand of nicotine, he had confessed to his family, even penning suicide notes per CBS News, which ultimately lead to his arrest.

Police said that around 2 a.m. on Nov. 1, 2005, Copple had entered the home via an open window and attacked Mazzara in her second-floor bedroom. Insogna, hearing the screams, rushed in and scratched Copple, leaving his blood at the scene, before he overpowered her. A third housemate, whose name was not released by law enforcement, escaped from her bedroom on the first floor and called police.

Speaking later to ABC News, the sole survivor of the killing spree said, "Still I can't sleep. Basically — it was a horror movie. That's what I thought — exactly what I thought when I was up there."

Police offered no motive — but perhaps even more chilling was that Copple had gone on to marry Lily Prudhomme, Insogna's best friend. When Lily was interviewed by 48 Hours about the killing — begging the public to come forward with any information — Copple was in the same room.

District Attorney Gary Lieberstein told CBS that he believed Copple was jealous of Lily's relationship with her friends and felt that any time spent with them "took away from their time together."

Lieberstein theorized that Copple had, in a drunken rage, killed the women after Lily refused to spend the night with him at their apartment.