Listen to your team as they will tell you how they feel. If you hear someone say something similar to "We're gonna die", check the team menu and see how he is doing. If there is an X across his face while he is shaking uncontrollably, bring out the Tazer and shock him. Wait for him to calm down, move out of the area, then give him back his gun. He might be bitter, but after you kill a few more things he will be fine. Otherwise, he might start shooting you and your team, ending with himself in the head.