A former New York City corrections officer was arrested Thursday for allegedly raping several women in Hempstead over several years.

Police say 42-year-old Ricardo Walters, already charged with a robbery, has been robbing women at gunpoint right on the street and sexually abusing them. They say the victims were typically undocumented residents.

Walters was indicted on 21 counts, including kidnapping, robbery, sexual abuse and rape charges for crimes dating back to 2005. He was first arrested last year after he allegedly robbed a 43-year-old woman at gunpoint while she was waiting for a bus. He was suspended in September from his job as a corrections officer.

Police say because the attacks are spread out over three years, there may be more victims who haven't yet stepped forward.

AP wire reports contributed to this article.