A Russian ex-police officer who was already serving time for the murders of 22 people was given a second life sentence Monday for murdering 56 other victims, NBC News reports. According to the outlet, Mikhail Popkov, also known as the “maniac of Angarsk,” was given his first life sentence in January 2015. But once in prison, Popkov confessed to 59 more murders, and provided investigators with enough detail to find his victims’ bodies and the weapons he used. All but one of his victims were women between the ages of 16 and 40. He was given a second life sentence for all but three of those confessions, making him one of the most lethal serial killers in modern Russian history. NBC notes that he joins the ranks of Andrei Chikatilo, who was executed in 1994 for killing more than 50 people, and supermarket employee Alexander Pichushkin, who killed 48.