Maksim Gelman discusses the four murders he committed in New York City in 2011.

Levi King kills two Missouri residents in 2005, then travels to the Texas Panhandle to continue his murderous ways.

A Missouri man kills two people at a friend's home, then continues the bloodshed when authorities come looking for him.

A "push-button killer" who served time for stabbing a woman unleashes his hidden rage on a new girlfriend.

A woman and her boyfriend, a convicted rapist, unleash their violent sexual fantasies upon two innocent victims.

Detectives in Great Falls, Mont., investigate the grisly stabbing death of a former corrections officer; the killer reveals his thoughts behind the crime.