Chapter: 2, Checkpoint: 2 [Fee Aim Enabled]
During your progression of chapter 2, you will find yourself in a nightclub which will result in having to jump through a window. As you jump through the window you will need to kill 6 enemies during the slow-mo dive, so quickly work out where the enemies are and shoot until you see the cross hit marker. You can do this on easy so your shots will do more damage.
Just take your time and learn where the enemies appear. They are always in the same places, so just remember where the ones you shot before were.
This video below will provide a visual aid in case you're having difficulty.