A 36-year-old man died after being severely beaten by a gang of youths inside the SEPTA concourse near City Hall this afternoon, police said.

One youth was taken into custody and police were still looking for three juveniles, possibly four, who fled the scene.

The attack happened at 13th and Market Streets on the concourse of a busy Septa stop about 2:45 p.m., said Officer Jillian Russell of the Public Affairs Unit.

SEPTA spokeswoman Sylvana Hoyos said a SEPTA police sergeant initially responded and administered CPR to the victim until medics arrived.

The Philadelphia Police Department's Homicide Division will investigate the death, authorities said.

Police said the SEPTA sergeant was on the eastbound side of the concourse when he saw the attack happening on the westbound side and immediately went to assist the victim.

The victim was taken to Thomas Jefferson University Hospital, where he was pronounced dead at 3:09 p.m., police said. Authorities are withholding his name pending family notification, but said he worked in Center City and was either arriving for work or on his way home after work.

A homicide detective said authorities were sorting through information surrounding the beating and expected to have more details available later.