A security guard was in critical condition after being shot Saturday at a Red Line station in Chatham on the South Side.

The man, whose age wasn’t released, was involved in a physical altercation with another man who pulled out a handgun and fired shots about 4:25 p.m. near the station in the first block of West 79th Street, Chicago police and the CTA said.

He suffered a gunshot wound to the neck and was taken to University of Chicago Medical Center, where he was listed in critical condition, police said.

A suspect was taken into custody blocks away and charges were pending. A handgun was also recovered, police said.

The CTA and police couldn’t confirm the security guard’s employment.