The video, recently posted at worldstarhiphop.com, shows an elderly man in a tan jacket wandering around passengers on the CTA platform. In the video, a group of teens is seen laughing and taunting the older man. A man, dressed in a black vest and hoodie, begins following the older man as the train approaches.

The train lets off passengers, and the younger man tries to get the older man's attention. The two talk briefly before he suddenly punches the older man, knocking him to the ground on his back. The older man's cap falls off in the blow.

Some teens in the group laugh and board the train. One of them mimics the punch, and as the train pulls away, a woman is seen checking on the man and calling someone on her phone.

The teen in the video has not been charged, according to police News Affairs.

Officers are looking for the victim, who was treated and released after the incident, to find out if he wants to press charges.

Source: http://www.nbcchicago.com/news/local/Teen-Punching-Man-at-CTA-Stop-Caught-on-Tape-133703583.html?dr#ixzz1dSnWpetK