I'm sure it's the real thing. He has a track record of getting the beheading videos up quickly.
Some Freeper on another thread commented on how all the beheadings are making us madder and more ready to fight rather than making up squeamish and scared. I guess that is the only possible positive to come of this. Yet, I am afraid that we will also get desensitized. I hope it never ever even approaches that point.