lol i think i know sargrass better than you. first make as much noise a possible, then hide and wait for him to come running with his silenced pistol(never fails). then shoot him with your gun of choice and watch his blood fly =) if that doest work for you, then get uav jammer/silenced gun/ and sneak around in crouch, till you find him and then proceed to blow his brains out. this to works =)
Of course, for either of these ideas to work you need a basic knowledge of hiding places on the map, a general idea of where he was last(its not that hard to figure out where some one spawns. hint
ther side of map), plus very fast reaction times(did i say fast? i meant uber fast). Luck helps alot.