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1:33 AM Wed, Nov. 21st

Thumb Butte murder remains a painful mystery

PRESCOTT – The morning of June 13, 1987, was warm and sunny, and Catherine Ann Sposito decided to bike to Thumb Butte for a hike up the mountain.

Catherine Ann Sposito was the victim of a brutal murder on Thumb Butte in 1987.

But what started as a pleasant outing turned into a tragedy when the 23-year-old Prescott College student became the victim of a brutal murder.

Today, exactly 15 years after Sposito's death, authorities are still searching for the killer. And those who knew her are still wondering why she died that day.

Investigators have not established a motive and have never arrested anyone in connection with Sposito's violent death, said Yavapai County Sheriff's Office Det. Theresa Kennedy.

The details surrounding Sposito's death remain sparse. She reportedly biked to Thumb Butte at around 7 a.m. that day. She chained her bike to a sign and briefly chatted with some other hikers. Witnesses reported that, about 20 minutes after she started up the trail, they heard a man and a woman arguing, a woman screaming and a gunshot.

Concerned hikers found Sposito's body before authorities arrived.

Sposito suffered a brutal beating. She had multiple wounds on her head, including lacerations and stab wounds and a single gunshot wound near her left eye. The medical examiner's report attributed her death to blunt force trauma, the gunshot and stab wounds and significant blood loss.

YCSO Det. Gordon Diffendaffer was the first investigator on the scene that day. He said that he remembers the case well.

"It was such a sad situation," he said, adding that the fact that they never found the killer has augmented the tragedy.