Experts weigh in on whether the 918 people, including almost 300 children, who died during the Jonestown massacre were victims of suicide or murder.

It's not uncommon for violence against women to reach a deadly peak on what some say is the most romantic day of the year.

Wayne Williams has been in prison for almost 40 years after being convicted of murdering two men. Although he was never tried or convicted, the murders of 29 kids and young adults were attributed to him as well.

People are trading bitcoin for goods and services on the illegal marketplaces of the dark web, where the easy, instant flow of the cyptocurrency allows users to tap into their darkest natures--all from the anonymous comfort of their home computers.

German serial killer nurse Niels Hoegel is suspected of killing more than 300 patients at two hospitals in Germany. Beatrice Yorker, an expert in serial killings in health arenas, tells us how killers in medical professions often get away with the crime.

Quite often it is only in hindsight that the friends and family of a mass-shooting perpetrator realize that the bloodbath was actually the climax of a series of foretelling clues from an angry, violent, paranoid, withdrawn person, who happens to have a  newfound fixation with guns. Such devastating epiphanies beg the question: Can we predict tomorrow's mass shooter?

Read an excerpt of the true-crime book "The Man From the Train: The Solving of a Century-Old Serial Killer Mystery" of the murder of the unorthodox Schultz family of Houston Heights, Texas.

Thomas Hargrove of the Murder Accountability Project talks about the 2,000 or so serial killers he believes are prowling U.S. streets now.

Why do so many killers—Jeffrey Dahmer, Ted Bundy and David Berkowitz to name a few—abuse animals before targeting people? An expert provides insights on how the two behaviors are linked.

Tommy Ray, a special agent with the Florida Department of Law Enforcement, came up with an idea that would revolutionize cold-case homicide investigations: making a game out of it.