there is a video of people reacting to the dead guy, once they realize. At first everyone is looking at the SS reaction, and if you don't understand how someone could freeze when they hear gun shots, I don't know what to tell you. Just watch any video of a shooting with bystanders. If they don't see a gun barrel pointed at them, they don't seem to react much.
I'm not saying there aren't some fishy things, I'm just saying the entirety of it being fake is unlikely