I guess you'd have to distinguish between being struck by panic and going berserk (like in Xcom). I agree that a panicking soldier would probably just cheese it or freeze in fear unable to do anything (zero TUs). A soldier who goes berserk on the other hand would shoot at anything he thinks might be an enemy. However, I think that shooting at any unit in sight is not necessarily a good solution for this. It would be more appropriate to limit this to new units that come into the FOV of the soldier. So if the soldier can see his team mates all along, he won't shoot at them. But if someone comes into his line of sight, for example a civilian popping round the corner, he just pulls the trigger in panic.