u can make new npc's,,,,
 or just script it,,,, i think it is like this,,,, 
 //(BHVD) 
 affect ( "stormie1", /*@AFFECT_TYPE*/ FLUSH )
 {
 set ( /*@SET_TYPES*/ "SET_DONTFIRE", /*@BOOL_TYPES*/ "true" );
 }  
 //(BHVD) 
 affect ( "stormie1", /*@AFFECT_TYPE*/ FLUSH )
 {
 set ( /*@SET_TYPES*/ "SET_DONTSHOT", /*@BOOL_TYPES*/ "true" );
 }    
 u can download behaved here (
http://www.jk2files.com/file.info?2888)   
 u dont need to use SET_DONTSHOT , that only makes npc's to not shot at the npc,,,, i think that will work,,,