AUSTIN, Texas - Thursday, December 29, marks the 25th anniversary of the death of a young Austin woman murdered by a serial killer.

That serial killer is suspected of murdering multiple people throughout Texas.

"This was one of the most heartless and brutal serial killers in American history," said author Gary Lavergne.

Lavergne remembers his interview with Kenneth McDuff vividly.

"I've never encountered anyone in the human form, anyone who was just so completely void of virtue," Lavergne said.

Lavergne wrote a book called "The Bad Boy From Rosebud," which tells the terrors inflicted by McDuff over 30 years.

"I did feel a responsibility as an author to bring this story to the public, to alert people to the reality that these guys exist," said Lavergne.

After murdering three teenagers in 1966, McDuff was put on death row.

When the death penalty was outlawed by the Supreme Court in 1972, his sentence changed to life in prison, making him eligible for parole.

Within days of his release in 1989, it's believed he started killing again.

Fast-forward to December 29, 1991: McDuff kidnapped 28-year-old Colleen Reed from an Austin car wash and later killed her.

"Anyone who has been in Austin for more than 25 years will remember this case," said Lavergne. "It was just so completely horrifying."

McDuff didn't stop there.

He was suspected of killing at least five other women while on parole.

Lavergne says his case shocked the state into action.

"Texas engaged in one of the largest prison building binges in the history of the free world," said Lavergne.

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Just before McDuff was executed in 1998, he led investigators to Reed's body.

According to Lavergne, it's likely McDuff is responsible for more deaths.

"He wasn't insane, he knew what he was doing, and he murdered his victims out in the middle of nowhere where no one could hear the screams," Lavergne said.

Nearly 20 years after McDuff's execution, Lavergne says his is a story that is still unthinkable.

"It's hard to believe that such people exist, but he did."

Lavergne is also the author of "A Sniper in the Tower," which details Charles Whitman's 1966 UT tower shooting.