Add occasional, non-player generated, gunshots in the Mix. Maybe one or two in a random room that echoes like a regular gunshot does.
Right now, gunshots are like beacons for players to sprint towards/from, but the Mix is supposed to be so violent and dangerous that gunshots would be mostly ignored as background music to existence.
Thinking of those war movies where massive explosions and gunshots are going off in the background, but the characters are so numb to it that they don't even give it a glance.
STREET SAM