Carl Panzram — a tattooed, 6-foot-tall giant of a man with cold gray eyes — stowed away on a ship bound for Angola around 1920 to work as a merchant seaman. After arriving in Lobito Bay, he hired a half-dozen local guides for a crocodile-hunting expedition. But Panzram had other prey on his mind. As their canoe wended its way down the river, he shot each crew member dead before feeding their corpses to the hungry crocodiles lurking below.

That was just one of many crimes, including 21 murders and more than 1,000 rapes of young boys and men, Panzram admitted to committing. Unlike charming and cunning serial killers Ted Bundy or Rodney Alcala, Panzram remained brutally honest. “For all of these things, I am not the least bit sorry,” he seethed in his autobiography, penned from his prison cell. “I hate the whole damned human race including myself.”

But could he really be that bad? Yes, at least according to experts who have studied him and found that the roots of his evil could be traced back to his childhood. Minnesota, Panzram’s father abandoned his family when he was about 8 years old. Soon after, Panzram landed in a reform school called Red Wing for a string of burglaries. Red Wing schooled Panzram in sadism, punishing him with beatings and rapes, which led him to a realization: “‘The world is this shithole, and I’m going to go through the world and wreak havoc in it,’” said Harold Schechter, a true-crime writer specializing in serial killers.

“Hurry it up, you Hoosier bastard!” he sneered at the executioner. “I could kill 10 men while you’re fooling around!”

After graduating, he spent years sleeping on freight trains. During one ride in a boxcar, he was gang raped by transients — leaving him “a sadder, sicker but wiser boy,” Panzram wrote. In 1915, he traveled through Idaho, California and other states along the Columbia River, burning and burglarizing buildings and raping countless young men and boys. Around the same time, Panzram was sentenced to seven years at the Oregon State Penitentiary for burglary. To punish his unruliness, the wardens hung him from the rafters for hours, turned a hose on him, and kept him in solitary confinement for weeks, leaving him to feed on cockroaches.

Not long after escaping in 1918, Panzram committed his first murders. In New York, he hired sailors to work on a yacht bought with his robbery bounty, lulled them to sleep with alcohol and shot­­­­­ them dead — all 10 of them. Soon after, he set sail for Angola, raping and killing a young boy before the crocodile-hunting expedition. About a year later, he hid aboard a Lisbon-bound ship, only to find that the police there were on the lookout for him, aware of his crimes in Africa. So, soon after, he stowed away on a ship to the U.S.

In 1928, Panzram was arrested for a series of burglaries and jailed in Washington, D.C. After a warden found out that he had tried to escape, the guards handcuffed and suspended him from a beam, beating him unconscious. Feeling sorry for Panzram, 26-year-old prison guard Henry Lesser handed him a dollar to buy food and cigarettes. “No one had ever been kind to him in his life,” said John Borowski, who directed the 2012 documentary Carl Panzram: The Spirit of Hatred and Vengeance. Over time, the two became friends. Each day, Lesser slipped him a pencil and a few sheets of paper, convincing him to write his life story.

Panzram was sentenced to 25 years at United States Penitentiary, Leavenworth in Kansas. There, he crushed laundry foreman Robert Warnke’s skull with an iron bar, landing a spot on death row and refusing human rights groups’ efforts to spare him from the gallows. After years of abuse, “it was his form of suicide,” Borowski said. Panzram got the death he craved in September 1930. “Hurry it up, you Hoosier bastard!” he seethed at the executioner — “rage personified,” as he referred to himself, until the end. “I could kill 10 men while you’re fooling around!”

Lesser kept Panzram’s writings, but publishers weren’t comfortable with the graphic manuscript until 1970, when it was published as Killer: A Journal of Murder. “The guy was really quite an amazing writer,” said Joe Coleman, who painted the cover art for the book, and who was “struck by the intelligence and the things [Panzram] could have been capable of.”

Beyond helping criminologists better understand the minds of killers like Panzram, Borowski said the autobiography serves as a lesson — one that still holds relevance amid recent reports of inmate abuse at Rikers Island and other prisons. “He tries to teach our future generations not to create more monsters like him,” he said, adding that Panzram, “above anybody else, should be listened to.”

This story was originally published on May 23, 2015.