I would assume a fired eventhandler can be used for both. Just put a fired eventhandler in the player's init field, and all the enemies' init field that sets a global variable to true, which in turn changes the combat mode of the other squad members, if that's possible, of course
-Student Pilot
EDIT:
Try something like this, in init.sqs, type:
AnyFired=false
Then, in the init field of all the enemy men and the player, put:
this addEventHandler ["fired",{AnyFired=true}]
Then, in a trigger, set the size to X: 5000 Y: 5000
Set the activation to Anybody Present
set the condition to:
this and AnyFired
and in the On Activation field, put:
group player setcombatmode "Red"; foreach thislist removeAllEventHandlers "fired"
Assuming of course changing the combat mode will do the trick. If it doesn't, just enter whatever works in the On Activation field, but keep the removealleventhandlers part.
Syntax not guarenteed.