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realize that the bloodbath was actually the climax of a series of foretelling clues from an angry, violent, paranoid, withdrawn person, who happens to have a  newfound fixation with guns.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.

The year 2017 was an explosive one on the crime-news front. But for the families of some long-ago crime victims, the past 12 months were especially memorable since their loved ones’ cases—some unsolved for decades—took dramatic new steps toward being solved

Why was Borden acquitted so quickly? And is there any relationship between Borden's rumored crimes and the homicides of other famed Victorian-era female killers like Belle Gunness?

Watch a video on wealthy murderer John du Pont, heir to the du Pont family fortune.

For some, the holidays are not the most wonderful time of the year. We look at several famous Christmastime murders and the psychology behind the killers to find out why such a merry time of year for some, can bring out deadly rage in others.