Maybe I should have mentioned that I enjoyed the advantage of seeing the whole scene unfold in the movie. Tom verbally challenged the 2 BGs from about 30 yards. The taxi was right behind Tom. After Tom's verbal challenge, the first BG drew his gun and walked the distance to Tom.
But still, looking only at the video as shown, the 2nd BG takes 3 or 4 steps backwards during the shooting before getting shot. (Count them, if you wish.) The 2nd BG had sufficient time to draw and shoot Tom. Unless, it's in the movies.