CROTONA PARK EAST - Police have released surveillance video of a man they say forced a 13-year-old girl to perform a sex act at knifepoint . 

It happened Thursday around 1 p.m. inside an apartment building near Jennings Street and Intervale Avenue.

Police say the suspect followed the teen into her Crotona Park East apartment building's elevator and coerced her into letting him inside of her apartment. 

Once inside, police say the man pulled out a knife and demanded money. They say the victim told the man she had no money, so he forced her to perform oral sex on him. The man also tried to rape the girl before running away with her backpack, police say.

Surveillance video from the apartment building shows the man who is described as being 18 years old, 5'8'' tall and weighing between 145 to 150 pounds. 

He was last seen wearing black pants, black slippers, white socks and a light-colored book bag, which police say belongs to the victim.

They say he was also carrying a red T-shirt or what appeared to be a towel over his shoulder. 

Anyone with information is asked to call Crime Stoppers at 1-800-577-TIPS.