AFTER THREE SIMILAR MURDERS, AUSTIN, TEXAS POLICE BEGAN TO WONDER IF A SERIAL KILLER WAS ON THE LOOSE - DID A MAN OUT FOR A LATE NIGHT WALK, TESTING HIS NEW THERMAL IMAGING NIGHTSCOPE, CAPTURE IMAGES OF THE ACTUAL KILLER?

"48 Hours" Investigates in "The Shape of a Killer"

Saturday, Dec. 21, 10:00 PM

After three murders with chillingly similar scenarios occurred in Austin, Texas, police began to wonder if they were chasing a serial killer. But whoever committed the crimes left no evidence, no DNA. Cops went into a frantic investigation. Suddenly, the hunt for clues changed, when a man testing out a new thermal imaging scope recorded the nighttime movements of a stranger. It was evidence cops never expected - and would help them break the case. Had a killer actually been filmed on his way to commit one of the murders?

Maureen Maher and 48 HOURS investigate the deaths of Kathy Blair and Billie and Sidney Shelton and the search for answers in an encore of "The Shape of a Killer" to be broadcast Saturday, Dec. 21 (10:00 PM, ET/PT) on the CBS Television Network.

It's a story that rocked Austin, a city that records few murders and is best known for its live music scene. The murders seemed senseless; the victims were all innocent, hard-working people, savagely killed at night in their own homes, in their own beds.

Kathy Blair was a beloved music teacher, a mentor and inspiration to hundreds of students and a conductor of a large Christian music choir. Billie and Sidney Shelton were elderly, frail, retired, hard-working Texans. They had all lived their lives honestly and well, and none of them had any known enemies. Investigators were in a race against time, convinced the killer might strike again.

"This is a case that sticks with you throughout your life," says Derek Israel, who was in the homicide unit for the Austin Police Department when the murders happened in 2014.

"I thought we were dealing with a serial killer," says Kerry Scanlon, who was the lead investigator on the murder of Blair.

48 HOURS and Maher go inside the investigation and see how police found their way to a totally unlikely suspect - a man with no previous criminal record - who proved to be a skilled and merciless killer. The trail turned on an unexpected confession and that one stunning clue investigators never expected: that high-resolution thermal video shot near Blair's home. It was recorded by Rob Leef, who lived a few blocks away from Blair, who just happened to be trying out a new thermal imaging scope that night.

The video was grainy and unclear. It did not reveal facial features. But it gave police one important clue that would prove to be critical later on.

"This video showed the murderer walking from the car towards Kathy Blair's house," Israel says. "The actual killer."

48 HOURS: "The Shape of a Killer" features interviews with friends and family of Blair and the Sheltons, as well as the two hard-working detectives who followed this case to the end. 48 HOURS also obtained prison interviews with two men: the killers who were ultimately convicted of these murders.

48 HOURS: "The Shape of a Killer" is produced by James Stolz and Jaime Hellman. Claire St. Amant is the development producer. Emma Steele is the associate producer. Mike Vele, Greg Kaplan, Joan Adelman and Michelle Harris are the editors. Peter Schweitzer is the senior producer. Nancy Kramer is the executive story editor. Judy Tygard is the executive producer.

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