No, Condition is the circumstances a trigger activates, basically they ask OFP a question like:
EG: not alive player
And when OFP answers that question it will check the On Activation.
EG : hint "You Are Dead"
So for your problem, using Tobruk's solution you shouuld create a trigger like this:
Condition : Man1 distance Sniper1 < 400
OnActiv : Man1 setdammage 1; playsound "Sniper"