Members of the Praetorian Guard were supposed to protect the Roman emperor — but they amassed so much power that they often assassinated emperors they didn't like.

A Presbyterian minister, Sylvester Graham believed that all of America's moral failings could be traced back to an unholy diet — and created a strict meal plan to "cure" society's ills.

In 1971, Donald Marshall Jr. was wrongfully convicted of killing his friend in Nova Scotia. And even after the conviction was overturned, he was still blamed for the judicial error.

On April 28, 1996, Martin Bryant pulled out an AR-15 rifle and began shooting indiscriminately at people in Port Arthur, Tasmania — and he didn't stop until 35 victims were dead.

On July 16, 2011, more than 60 people came to 17-year-old Tyler Hadley's house and partied for hours — unaware that his parents' corpses were hidden just behind their bedroom door.

In June 1969, Dennis Lloyd Martin walked off to play a prank on his dad and never returned, sparking the largest search effort in the history of Great Smoky Mountains National Park.

In 1944, Finnish soldier Aimo Koivunen got separated from his unit and survived for weeks inside the Arctic Circle without food or shelter — fueled by a dose of meth large enough for 30 men.

Just days after her 24th birthday in August 2015, Alison Parker and 27-year-old cameraman Adam Ward were murdered in the middle of an on-air morning interview which was broadcast in real time.

Known as the "eighth wonder of the world," the Amber Room at the Catherine Palace in St. Petersburg was looted by the Nazis and disappeared forever in 1943.

Known among the Nazis as "the girl with the red hair," 24-year-old Hannie Schaft was so deadly that Adolf Hitler personally ordered her capture.

In 1919, Black sharecroppers in Arkansas tried to organize for better wages — until a white mob and U.S. troops murdered hundreds of them.