From the laughing epidemic of 1962 to the killer clown scare of 2016, these cases of mass hysteria show just how bizarre — and dangerous — this psychological phenomenon can be.

Thirty-year-old Sabrina Kauldhar senselessly murdered her victims in a series of sudden attacks across multiple cities in Ontario starting on October 1.

The silver coins feature images of rulers like Edward the Confessor and Canute, the Viking king who united England, Denmark, and Norway under the North Sea Empire.

Christopher Reeve, the actor who rose to fame as Superman, fell from his horse in 1995, broke two vertebrae in his neck, and spent the rest of his life in a wheelchair.

Ilya Repin's 1885 painting "Ivan the Terrible and His Son Ivan" shows Ivan IV, the first Russian czar, cradling his dying son after bludgeoning him, but historians are divided as to whether this murder ever really happened.

Dating to the 5th century B.C.E., Gela II measures approximately 50 feet long and 16 feet wide, which enabled it to carry large amounts of cargo, including the mythic metal orichalcum that's been linked to Atlantis.

Six-year-old Morgan Nick vanished from a Little League ballpark in Alma, Arkansas on June 9, 1995. Now, more than 29 years later, police have found DNA evidence linking Billy Jack Lincks to the disappearance.

Just minutes into their planned three-day search, two maritime historians discovered the wreckage of the tugboat John Evenson 42 feet beneath the surface of Lake Michigan, where it sank in 1895.

In 125 B.C.E., the ancient city of Fregellae in modern-day Italy was destroyed when it rebelled against Rome. Now, archaeologists have uncovered evidence of this violent revolt, including fire-damaged structures, a military camp, and signs of economic devastation.

While the ancient dairy product was described as "really dry, dense, and hard dust," it was once soft kefir cheese made from the milk of both cows and goats.

Researchers theorize that woolly mammoths may have gone extinct due to pollen allergies triggered by climate change, which impaired their ability to find mates, detect predators, and locate food.