End#1 and End#2 both lead to the same Outro. You could use ending type Loose for one of them but then you get no Debriefing text.
You must make it very clear to the player what he is supposed to do.
Add an eventHandler "killed" to the civvy. If his killer is not the player, then something else happens. If his killer is the player, then the script called by the EH checks the value of a variable. This variable is initialised (say, set to false) in your init.sqs then set to true when the civvy fires. If its false when the civvy dies you get the mission failed ending, if its true you get mission accomplished.