Karol Kot was born on 18 December 1946 in Krakow, Poland.
His father was an engineer for the army and his mother was an activist for the League of Women.
Karol’s parents came from well educated families and provided their son with a good life.
From an early age Karol exhibited disturbing tastes. As a child he would torment small animals.
During summer trips he enjoyed visiting a local slaughterhouse to see the animals being killed.
He often helped to kill the calves and had a bizarre habit of drinking the warm blood of the freshly killed animals.
He also killed frogs, chickens and magpies. Sometimes he would stop his mother from killing fish, only to poke their eyes out and lick the blood off them.
As a teenager, Karol tried to enroll at college, but a lack of places meant he did not get in.
He eventually got a place at the Technical Energy School in Krakow where teachers found him to be a good student.
During high school he joined a shooting club and quickly became his coach’s favourite student.
At one point he was ranked tenth in the Polish juniors category for the sport.
Karol’s coach even gave him the role of deputy for economic affairs at the club, allowing  him to carry the keys to the weapons and ammunition store.
"I could slay the whole of Krakow," he confided to a journalist after being aprehended.
The coach invited Karol to his home, trusted him, and set him up as a good role model to his son.
However he did not realize that his son was already on Karol’s list of potential victims.
It is not known whether Karol decided against murdering his coach’s son or whether he was caught before he could carry out this plan.
After Kot’s arrest, the coach sent a letter to the Ministry of Justice, in which he protested the arrest.
Later, when he finally realised that his favourite pupil really had committed these crimes, he sent Kot a letter full of indignation and regret, in which he asked him to return his sportsman badge because he was unworthy of the title of athlete.
Another of Karol’s fascinations were weapons and torture, or, as he said once said himself, “everything that serves for human destruction”.
He had an impressive number of knives in his collection. Grateful that their son had an interest, his parents were happy to give him money to buy new knives.
Using an air rifle that he kept in the house, Karol used to shoot meat which his mother had bought for dinner, just to experience the power of the bullet.
Karol loved reading books on human anatomy and toxicology, and he had knowledge of forensic medicine.
He was also fascinated by the history of concentration camps.
“I dreamed about mass murder in gas chambers, roundups, dividing people. I wanted to murder all women”.
Living with Karol was hard on his younger sister. When their parents were away he would physically and mentally abuse her.
After a disappointing day at the shooting range, he would beat her to relieve his frustration, with anything from a hand strap to a belt and even with a coat hanger. Once, he almost poked her eye out. When she cried, he would lock her in a room.
In school, Karol experimented with poisons.
He once poured arsenic into a classmate’s drink but because this gave the drink a bad smell he poured it away without tasting it.
Karol would also fill beer bottles with arsenic and leave them lying around to tempt random members of the public. Luckily, no one was tempted.
He also tried a similar poisoning attempt in a restaurant by spiking a glass of orange juice, but again, no one was tempted by the drink. 
Karol’s murderous interests continued to grow.
He had always been fascinated with fire and developed this interest by trying to set a house alight. However, when he returned to see how much damage the fire had done, he was surprised to find that there was not even smoke. In the basement of another house he set fire to some rags and loose papers - again without effect.
He later tried to set fire to a wooden toilet at the shooting range, but a caretaker managed to extinguish it.
Despite his popularity among the teaching staff at school, Karol was not so well-liked by his classmates.
He was quiet and withdrawn, almost morbidly shy.
The only person he trusted, who tried to understand him and felt comfortable in his company, was Danuta, an older girl from his sports club.
She was a student at the Academy of Fine Arts.
He confided all his secrets and aspirations to her, but she initially she did not take his sadistic tendencies seriously.
In the winter of 1966 Kot confided to Danuta that he found inflicting wounds pleasurable. This confessions to would later become very useful to the investigation when Danuta raised her suspicions with the police.