This works in every missions, whenever you die the fist thing that happens is the screen starts to turn red and everything goes in slow-mo.
When that happens shoot threes guy in the head (it won't work if you hit them anywhere else or if you miss).
If done correctly you will come back to life but your health will be 0, so use your painkillers quickly.
Once you die again it won't go in slow-mo, you will just die