Gary Michael Heidnik kidnapped, raped, and tortured six women starting in 1986, keeping them prisoner in the basement of his Philadelphia home.

These tragic photos and stories capture the horrors of the Nanking Massacre — a.k.a. the Rape of Nanking — committed by Japanese soldiers against Chinese civilians.

In 1965, Sylvia Likens and her sister Jenny were left in the care of family friend Gertrude Baniszewski — who tortured Likens to death and got her own children to help.

From 1961 to 1971, the U.S. used the herbicide and defoliant Agent Orange in Vietnam, leaving behind millions of victims with deadly diseases and birth defects.

On August 14, 1980, Playmate of the Year and budding actress Dorothy Stratten was gunned down by her estranged husband. She was just 20 years old.

An 18th-century French showman, Tarrare could eat enough to feed 15 people and swallow cats whole — but his stomach was never satisfied.

On a busy Saigon street in June 1963, Buddhist monk Thích Quảng Đức lit himself on fire and set off a chain of events that led to America's involvement in the Vietnam War.

For 30 years, Boy Scout troop leader and church council president Dennis Rader was secretly the BTK murderer — while looking like the perfect family man to his neighbors in Kansas.

In May 2012, Luka Magnotta murdered a university student named Jun Lin, chopped up his body, and mailed his limbs throughout Canada, then shared a video online of his crimes titled "1 Lunatic 1 Ice Pick."

Despite his mythic handicap, Ivar the Boneless was the most fearsome Viking of his time and conquered England with his heathen army.

Known informally as the Japanese mafia, the Yakuza are a 400-year-old criminal syndicate that carries out everything from human trafficking to real estate sales.