Yong was executed by a firing squad on 26 December 2003, after 17 corpses were unearthed from his backyard. He mostly targeted young boys as he believed old men were too vigilant to trick, and female victims would make him look like less of a "hero".
2. The Russian killer Alexander Pichushkin was nicknamed the "Chessboard Killer" because his goal was to kill 64 people, which is the exact number of squares on a chessboard.
3. Niels Hoegel, a German nurse, intentionally injected his patients with drugs to cause heart failure, because he liked showing off his resuscitation skills to colleagues.
Niels was already serving a life sentence for murdering two patients, when in January 2018 he was again charged with 97 murders. He was first caught after a nurse observed that a previously stable patient had a stroke during Niels' shift. The nurse later found empty medication containers in the wastebin while he was busy resuscitating the patient.
4. Professor Mohan Kumar, aka "Cyanide Mohan", lured young women into marrying him and killed them the next day by giving them birth control pills laced with cyanide.
5. Leonarda Cianciulli from Southern Italy converted her three middle-aged victims into soap and cake, which she gifted to her friends later.
After a fortune-teller predicted all her children will die, Leonarda believed sacrificing others' souls would keep her kids safe. She died at age 76 after being sentenced to 30 years in jail.
6. On 16 March 2000, a Pakistan court sentenced Javed Iqbal, a murderer of 100 boys, to be strangled to death with an iron chain, diced into pieces, and dissolved in acid the same way he killed his victims.
Before Javed could be punished, he was found dead in his jail cell under mysterious circumstances on 8 October 2001.