Updated

New York City police are looking for a 28-year-old registered sex offender wanted for questioning in three robberies, including one where a German tourist was beaten and sexually assaulted.

Chief of Detectives Robert Boyce says the man, whose name was given as Keon Robinson, was last seen going into an East Harlem building following the attack on the tourist early Thursday morning.

Surveillance video shows a man punching the woman's head and continuing to hit her after she falls to the sidewalk.

Police say the man also punched the ground and they believe he left a trail of blood.

Police say no sex assault occurred during the other two robberies.

Police asked that anyone with information call the tips hotline at 1-877-8477.