Clifford Robert Olson Jr. was a convicted Canadian serial killer who confessed to murdering 11 children and young adults between the ages of 9 and 18 years in the early 1980s. Olson scored 38/40 on the Psychopathy Checklist.
The bodies of the three boys and eight girls, aged between 9 and 18, had been found in secluded areas within a 90-kilometre radius of Vancouver. Some of the victims had been raped and sodomized, some were bludgeoned, others were stabbed and one was strangled. All had been drugged and killed in a murderous spree lasting only nine months, from November, 1980, through July, 1981, while Olson was out of prison on mandatory supervision!