Chicago (CBS) — Detectives hope CTA surveillance cameras will help them catch the group of robbers who beat a passenger on a Red Line train early Sunday morning.

Police say a 42-year-old man was riding near the Belmont stop around 2:30 a.m. When the victim encountered a group of noisy people and asked them to move, they started punching and kicking him.

One of the robbers pulled out a knife and demanded his possessions.

The victim suffered bruises and cuts to his face.