A Brazilian man arrested by police on suspicion of a stabbing a woman, allegedly confessed that he is a serial killer who murdered 42 people in and around Rio de Janeiro.

Reuters noted that on Wednesday, Sailson Jose das Graças, 26, told reporters at the police station that he killed dozens of people over the span of about nine years.

Gracas claimed that his alleged victims were mostly white females, who he studied and followed for months before breaking into their homes and strangling them.

“I would wait for an opportunity to break into the house and kill,” he said. “When I didn’t do it I would get nervous, then I would go hunting.”

The alleged murderer said that in addition to the woman, he killed at least two men and one small child.

Investigators are trying to get in touch with the families of those who were murdered and said that as of Friday, they have evidence linking Gracas to four of the slayings.