The Megatherium roamed South America for 5.3 million years before it went extinct — though some Indigenous people claim to have seen a similar creature in the Amazon to this day.

In less than 100 days, Finnish sniper Simo Häyhä killed at least 500 enemy troops during the Winter War — earning him the nickname the "White Death."

In 1979, 16-year-old Brenda Spencer shot up an elementary school in San Diego — then said she did it because she didn't like Mondays.

Almost 500 years after the society crumbled, researchers have finally discovered what happened to the Aztecs.

Made famous as Jimmy "The Gent" Conway in "Goodfellas," real-life New York gangster Jimmy Burke was even more ruthless than his onscreen counterpart.

Anne Bonny and Mary Read were a pair of cross-dressing pirates, who became the fiercest female pirates in the Golden Age of Piracy.

"Silent twins" June and Jennifer Gibbons spoke only to each other, used their own special language, and mirrored each other's behavior for three decades straight.

After John List murdered his wife, mother, and three children in 1971, he assumed a different identity, remarried, and started a new life — until an episode of America's Most Wanted finally led police to him in 1989.

When a fire erupted inside the coal mine in Centralia, residents thought it would quickly burn out on its own. But the blaze is still going six decades later and the state has given up on trying to fight it.

Bruce McArthur brutally murdered eight gay men between 2010 and 2017 — then hid their remains in potted plants.

In the late 19th century, Amelia Dyer took in untold numbers of babies for a fee, promising their desperate parents she’d use the money to take good care of them. Instead, she pocketed the money — and brutally murdered the children.