A former Russian police officer has reportedly been convicted of 56 murders while he was already serving a life imprisonment sentence for 22 killings. According to a statement from the prosecutor's office in Irkutsk, the former cop, identified as Mikhail Popkov, is believed to be Russia's most prolific recorded serial killer and was convicted on Monday for murdering at least 56 people between 1992 and 2007.

Reports state that Popkov is known to kill his victims with screwdrivers, axes, knives or blunt weapons after offering them rides home late at night. The former cop would take his victims in his police car sometimes while wearing his uniform. Popkov is often dubbed as “The Werewolf” and the “Angarsk Maniac” by Russian media and is known as the country's worst mass killer, with a total of at least 78 murders.

The murders reportedly occurred while he was off duty and close to his home city of Anagarsk and the killings continued for almost a decade after he left the police force in 1998, according to Newsweek.

The accused was convicted of killing 22 women and was sentenced to life imprisonment. Later, Popkov reportedly also admitted to killing an additional 59 people. According to the Interfax news agency, the prosecutors have only been able to prove his connections with 56 killings. 

All of his victims are allegedly women between the ages of 16 and 40, except for one man who was a police officer too. Popkov reportedly mostly targeted women who had been drinking or prostitutes, as he considered them immoral, according to the Siberian Times.

Prosecutor Alexander Shkinyov said that Popkov decided to kill the women "as soon as they agreed to share a drink with him," he reportedly committed the crimes after being under false suspicion that his wife had cheated on him. Shkinyov added that Popkov showed "a pathological attraction to killing people.” He was also found guilty of sexually assaulting 10 of his victims.