A 12-year-old Staten Island boy spending the day with his grandmother at the South Street Seaport told authorities he was sexually assaulted in a bathroom near the pier shops Tuesday evening, police said.

The boy told police he went to use the bathroom as he and his grandmother got ready to leave the pier; he said a man pulled him into the one of the stalls and performed a sexual act on him, police said.

Once he was back outside, the child told his grandmother that he was "raped in the bathroom," police sources said, and investigators were called to the seaport.

Police Commissioner Ray Kelly said detectives are working to create a sketch of the suspect based on the boy's description, and video from seaport surveillance cameras around the time of the assault will help them identify a suspect. 

Some surveillance  cameras were damaged by Sandy, Kelly said.