Thread:Comments:Four people shot in parking lot of Wal-Mart store north of Austin, Texas/Comments from feedback form - "Facial wounds,no customers or ..."/reply

Learn to read. "Four, including the gunman who had facial wounds, are being treated ..."

This is a common use for the comma; to separate a clause without which the sentence could stand alone. You have read as-if the comma was placed after the word gunman.