two ways of doing. in both cases you need the command
this setCaptive true
in the loon's init field .... when you want East to shoot him you need a trigger
on activation: loon1 setCaptive false
1) create a civilian and a West soldier. The West soldier is the group leader. Delete the West soldier at the start of the mission and hey presto the civvy will be regarded as West by the AI ... except that he is setcaptive
2) Edit the mission.sqm file. How to do this has been well covered on this board already and is probably in the FAQ too.