A 19-year-old woman waiting for an elevator inside a Bronx apartment building was threatened by a stranger demanding sex for money, then assaulted when she tried to run away, police say.

Police are now searching for the alleged attacker, who was captured on surveillance video approaching the victim inside the building near Aqueduct Avenue and West 190th Street in Kingsbridge just after midnight on Tuesday. 

When the victim refused the man's demands, he threatened to kill her if she called 911, police said. The woman ran out of the building, and the suspect chased her and grabbed her hair, choking and struggling with her, video shows. 

The suspect then ran away, going south on West 190th Street, according to police.

The victim sustained minor injuries. 

Anyone who recognizes the suspect is asked to contact Crime Stoppers at 800-577-TIPS.