It was a horrific crime, even by the big-city standards of Houston. On the afternoon of July 18, 2003, two people entered a home in the manicured suburb of Clear Lake and shot to death the four young people inside. There were no obvious suspects. No arrests were made.
Police worked the case for three years. They interviewed dozens of the victims' friends and acquaintances, many of whom were classmates at Clear Lake High School. They fielded hundreds of tips, none of which panned out.
Family members of the victims pitched in. Leading the effort was George Koloroutis, father of victim Rachael Koloroutis, who was 18 when she died. He printed fliers, sent out mass mailings and went door to door to raise more than $100,000 for a reward in the case. Koloroutis also arranged for composite sketches of the potential suspects to be released to the public and posted on more than a dozen billboards along Houston freeways.
"He was able to think with his head when all I wanted to do was think with my heart. But George never gave up," said Ann Koloroutis, Rachael's mom, in an exclusive interview with "20/20."
"I thought that would have a really meaningful and loud impact on the community," said George Koloroutis of his efforts. "And it would ... make these killers come out from hiding."
Then, in July 2006, a tipster called a police hotline with details only an insider could have known. He knew the position that Rachael, a recent high school graduate, had died in. She had been crawling on the floor. A phone lay near her hand. She was trying to dial 911.
"This is your shot," Houston Police Sgt. Brian Harris told ABC News, recalling the moment. "This is our one shot to make this happen."
The tipster mentioned two perpetrators. One was shrouded in mystery; the tipster thought his name was Chris.
There was no question about the other perpetrator. She had seemingly told the anonymous tipster everything about the crime. She had been a classmate of Koloroutis and another victim, Tiffany Rowell, at Clear Lake High School. Her name was Christine Paolilla.
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The police hunt, arrest and trial that followed shocked the victims' families, the high school and the greater Clear Lake community. Christine, Rachael and Tiffany, it turned out, were more than classmates. For a while they had been close friends. Also killed were Tiffany's boyfriend, Marcus Precella, and his cousin, Adelbert Sanchez. The looming question was what, exactly, had gone wrong -- and why it all had ended in such violence.
Clear Lake High School attracts kids of oil executives and NASA engineers. And in the inevitable social hierarchy that exists in any high school, Rachael Koloroutis and Tiffany Rowell stood on top.
Tiffany was a talented actress who dreamed of becoming a social worker. Rachael was into art and creative writing. Like Tiffany, she was blessed with the two things every teen craves: good looks and popularity.
"When you first saw Rachael Koloroutis, she just struck you as this beautiful girl," said Jennifer Grassman, a friend. "I mean, she could have been a model."