BROOKLYN - Police are asking for the public's help finding a man who allegedly sexually assaulted a 14-year-old girl on the Q train. 

The NYPD has now released photos of the suspect, who it says followed the victim onto the train at the Church Avenue station back in January. 

According to investigators, the man sat down next to the teen and rubbed her inner thigh, then followed her again when she got off the train. 

They say the man fled once 911 was called, but the girl was able to identify him from social media sites. He's described as having dark hair and a slender build. 

Anyone who can help should call Crime Stoppers at 1-800-577-TIPS