I don't know where the heck you found this "HIT_TARGET" thing!
Look into the manual for the event handling and the different events.

http://www.conitec.net/beta/aevent_entity.htm

EVENT_ENTITY should do the job for you, because it returns 'you' as the pointer to the touched/hit entity, and then you can 'ent_remove(you);'.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt