I think I would just get as close to the floor as possible and be motionless as possible with flashlight out and off with pistol in hand. Waiting for him to come to me. At least in the first few chaotic moments. If I could determine there was a pattern to the shooting, I might try to move to safety. I am probably not going to know he is wearing body armor, and if I did get a "good" set of shots off would have probably ended up dead anyway.