Heres my code:
area
looserock
icon = 'cliffs.dmi'
proc
nboulder()
var/obj/B=new/obj/boulder
B.loc = locate(/area/looserock)
walk(B,SOUTH)
spawn(50)
nboulder()
obj/boulder
icon = 'boulder.dmi'
density = 1
Bump(mob/M)
M.loc = locate(3,3,1)
M.rhealth = M.health
M << "You were crushed by a falling boulder!"
del(src)
See if that helps.