If it was a situation, (like in the vid), where it was some guy strangling another guy on the ground like that...
I would think that anyone could just kick the guy in the head as hard as they could, pull the victim away, run outside of the elevator and find something that could do some damage, beat the douchebag over the head with it, take the rope (or whatever the hell that was that he was using to strangle the guy with) hog-tie his ass, then call 911.
(Why yes, I do enjoy watching action movies, thanks for asking)
If he had a gun or a knife though... Eh, nope, see ya. Run away, dial 911.