When Brazilian police arrested Sailson Jose das Gracas Wednesday, after he allegedly stabbed a woman to death, they got more than they bargained for—much more. Das Gracas ultimately confessed to murdering another 41 people in Rio de Janeiro since 2005, 37 of them women, three men, and one a two-year-old girl, the BBC reports. He told police he watched his alleged victims for weeks or months, waiting "for an opportunity to break into the house and kill," and says he wore gloves and a rain jacket to help disguise himself. The 26-year-old said he would often strangle the women he killed, but that the men were killed when he was murdering for hire, and in those cases he used a gun.
Police have started cross-referencing his confession with existing police reports, and say they have confirmed four of his alleged victims so far. If his confession proves true, he would be one of the country's "most prolific serial killers," Sky News reports. Officers say das Gracas told them he killed for the "fun of it," and experts say he appears to be a psychopath who is enjoying the attention he's receiving—so his confessions should be carefully investigated, they warn. He also warned police he would murder more people if released. A disturbing detail: The Independent reports that das Gracas said he often removed his victims' fingernails. (Another Brazilian 26-year-old recently confessed to 39 murders.)