After Erin Caffey's parents told her she couldn't see her boyfriend anymore, she sought revenge — by having her family brutally murdered in their sleep.

On December 18, 1994, Alison Botha was abducted near her home in South Africa. By the end of the night, she had been raped, stabbed, and disemboweled — but somehow, she managed to live.

Known as a "nice guy" who was able to charm countless women, Shawn Grate was eventually revealed to be a brutal killer who murdered at least five victims.

Until his arrest in 2015, Peter Scully sold videos of himself torturing and sexually abusing young girls on his dark web site "No Limits Fun."

Starting in 1987, the suburbs of Melbourne were terrorized by a rapist known as Mr Cruel whose attacks were so carefully planned that he left not a single trace of forensic evidence behind.

In 2000, Dr. Harold Frederick Shipman was convicted of murdering 15 of his patients, then he killed himself inside his prison cell just four years later.

Sixteen-year-old Cassie Jo Stoddart was murdered by two of her high school classmates while house sitting in Bannock County, Idaho on September 22, 2006.

In the 1960s, Eric Edgar Cooke murdered at least eight people in Perth and sometimes even dabbled in necrophilia — until he was finally caught.

In 1974, Randall Woodfield was drafted and quickly dropped by the Green Bay Packers. Just a few years later, he went on a brutal murder spree — killing up to 44 people.

On February 17, 2014, 14-year-old Breck Bednar secretly met 18-year-old Lewis Daynes at his apartment in England. Bednar was found dead the next day.