UNITED NEWS INTERNATIONAL (UNI) — A former policeman in Russia who killed 22 women has admitted to an additional 59 murders.

Russian news agency Interfax said Mikhail Popkov recently went on trial for the newly-confessed killings in the Siberian city of Irkutsk.

Prosecutors reportedly claim Popkov killed his victims and alleged victims in the nearby city of Angarsk between 1992 and 2010. He served on the police force for several years during that time.

All but one of his victims were female between the ages of 16 and 40. He allegedly lured them into his car and killed them with an ax or a hammer.

Russian media dubbed him “The Werewolf” and the “Angarsk Maniac.”

He was arrested in 2012 and convicted in 2015 of raping and killing 22 women.

Popkov is already serving a life sentence. If convicted of these additional murders, he would become the most prolific serial killer in Russia’s recent history.