Two parts to this question.
Firstly, the condition line of the trigger - in other words, who is getting shot. You can detect this in various ways, depending on what you are trying to do.
(not alive loon1) or (not alive loon2)
or
(count units grp1) + (count units grp2) < 11
If you have say East present in the Activation box then you might have
count units thislist < 15
Secondly, the On activation line of the trigger. You could havea switch trigger switching the relevant groups into a new waypoint and not bothering with an on activation line. Alternatively, you could have something like
"_x setBehaviour {aware}" forEach thislist
in which case you would need to have the Activation box set to east/west present, whoever you wanted to go aware.
Syntax not guaranteed.