The video shows you how to keep Sgt. Johnson alive after the cutscene where he dies. You don't need to do the trick to get his spartan laser, but you do need a weapon that can kill him in 1 shot and the spartan laser is the best choice. Basically all you need to do is kill him before you enter...

containse the following -Walkaway chainsaw -Firefly Glitch (Fully auto weapons) -Rambo Glitch (made by us) -Kung-Fu Backfilp -Lancer Backflip -Host Slide -Rodie run (crab walk) -Shotty Chainsaw -Remote chainsaw -Invisable man (Revised) -Airwalk -Host shotgun glitch -Out of Fuel Depot -Out of...