World's Most Evil Killers Season 6

John Allen and Lee Malvo: The story of the Beltway sniper attacks. John Allen and his teenage accomplice carried out the brutal series of shootings that killed 10.

The story of one of the most prolific serial killers in Canadian history, dubbed `The Pig Farmer Killer' by the media.

The story of the serial killer Sean Vincent Gillis, who brutally snatched away the lives of eight innocent women during a decade-long killing spree in Louisiana.

The story of a terrifying killer who snatched away the lives of four victims before being caught while trying to claim his fifth.

The story of Judy Buenoano, the first woman in Florida to die in the electric chair. She was a killer so evil that her own son became one of her victims.

Serial killer Gary Ray Bowles, who took the lives of six men in 1994, and became known as the I-95 Killer, as most of his victims lived close to the Interstate 95 highway.

A profile of Derrick Todd Lee, who murdered seven women in the Baton Rouge area of Louisiana, and was sentenced to death for his chilling crimes.

The story of Velma Barfield, the first woman to be executed by lethal injection after taking six lives.

The story of the cold-blooded serial killer who took the lives of at least fifteen people during a terrifying decade-long murder campaign.

The chilling story of the serial killer who worked as a nurse in Texas, where she killed many children and infants by injecting them with drugs.