I watched the video several times and it clearly shows you missing your second and third shot. If you pause at 0:09, it shows your shot going to the right of the player. Then you miss your final shot by shooting directly under the enemy player. You can clearly tell you missed your shot. What I noticed you doing is you tend to shoot then aim your shotgun. If you pause around the 10 second mark (at the perfect time) it clearly shows you shooting under him/her.