HH Holmes was married to three women at the same time, all under different identities. He was accused of killing 27 people in his “murder castle” hotel.

Experts estimate there are at least 2,000 serial killers roaming free in America

Ted Bundy once saved a young boy from drowning. He also chased down a purse thief on the street. He was convicted of over 30 murders.

Experts categorize serial killers by type, including… Missionaries: Killers who feel it is their duty to rid the world of people they find immoral or undesirable. The victims of Missionaries usually include drug addicts, prostitutes, or immigrants

Angels of Death: Nurses who kill their patients. Nurse Genene Jones is suspected of killing up to 60 Texas children

Black Widows: Women who kill men, usually to inherit money or claim insurance. Mary Elizabeth Wilson killed four husbands and inherited each of their properties

Bluebeards: Men who kill women, usually for money or assertion of power. George Joseph Smith killed three wives and reaped financial rewards from each of them.

Troller: Meets a victim by chance

Trapper: Either carefully observes victims before killing them, or works somewhere that victims come to them, like a hospital.

Jeffrey Dahmer pulled so many pranks in high school, they called it “Doing A Dahmer.” He murdered 17 people, cannabalizing some of them.

Oh, and here is a photo of Dahmer’s signature in a friend’s yearbook from Freshman year of high school. It reads: “To Ted, The most idiotic foolish person I know but nice kid — Jeff Dahmer”

Here’s his yearbook signature again from Junior year (notice the drastic change in handwriting): “Hello Ted, how are you? Have you partyed much? I hope things go well for you and you are not discovered as a commi! — You Know Who” (Ted wrote “Jeff Dahmer” himself so he would remember who “You Know Who” was years later).

The Murder Accountability Project (MAP) is a computer algorithm designed to find serial killers based on the locations of murders and how each murder was carried out. Atlanta police are currently using MAP to trace the murders of 40 women in the area, all strangled to death.

Dennis Rader, known as the BTK (Blind, Torture, Kill) Killer, worked for ADT Security Services installing home security systems. He worked there for 14 years while murdering 10 people in his spare time.

When Alabama reinstated capital punishment in the late 1960s, no one knew how to operate the electric chair. As a result, the first man they put to death was accidentally burned alive. Said one journalist on the scene: “Everyone was crying, and I had trouble sleeping for days after.”

Richard Chase believed he could absorb vitamin C through his brain by placing oranges on his head. He shot and killed six people, raping two of them post-mortem.

In the 1960s, a killing led to an arrest 92 percent of the time. Today, a killing only leads to an arrest less than 60 percent of the time.

Though many names on this list would be an exception, serial killers aren’t typically as bright as most people, with an average IQ of 94.5 (The American average is 98). Take Otis Toole, whose partner in crime called him the “worstest killer in the world.”

Marcel Petiot was the mayor of Villaneuve, France. During WWII, he offered fleeing Jews refuge, then gave them a shot which he said would prevent disease. It was actually poison. He kept the corpses in his cellar and confessed to killing over 60 people.

Rodney Alcaca won The Dating Game, but the woman refused to go on their date, finding him “creepy”. He is suspected of killing 130 people.