Make a trigger:
OnActivation: KillThePlayer = Player AddAction ["Kill me!","Kill.sqs"]
OnDeactivation: Player RemoveAction KillThePlayer
Save your mission.
Now open notepad, save it as Kill.sqs (make sure it is Kill.sqs not Kill.sqs.txt)
And put in it: Player SetDammage 1
Press ctrl+s and go back to your mission.
Walk into the trigger, and see what happens!
Good luck