Can't see what happens when the one guy picks up a chair, could have been ugly LOL
It appears to me that the gentleman with the chair is the individual who was initially attacked, or at least, the first individual we see attacked on the film. It further appears that he was being attacked by two other gentleman, and one of those gentleman was wearing a jacket and a T-Shirt such that the bottom of the T-Shirt was below where the jacket stopped.
After the initial attack, the gentleman writhed around on the floor a bit and eventually found himself up against a bar stool. That gentleman then eventually got up, (after the two other gentlemen, I presume, had been pulled a few feet away) and attempted to pick up the bar stool after dragging it a foot or two to an open part of the floor. The gentleman dropped the bar stool on his first attempt to pick it up, shortly after which time it appears that the guy with the T-Shirt that stopped below his jacket decided to leave the scene, almost immediately after that, then gentleman who was initially accosted in the video finally managed to pick up the bar stool. It sounds like he threw it and hit something unrelated, or hit a person and then the stool hit the floor or something unrelated.
The mechanics of a bar stool are such that it is a very ineffective weapon, so it is unlikely anyone got seriously hurt by it. A bar stool is the type of weapon that, short of throwing it at an unsuspecting target or someone with his back turned, it'll probably get taken away from you or you will determine it is a useless weapon before you do anything with it.
If you were to swing a bar stool by the legs, or a leg, given the distribution of the weight (with the heaviest part, the seat, the furthest away from you) chances are you're not going to build up enough velocity to achieve a meaningful strike, that and the fact that the person would be getting hit with a piece of upholstery....It would, at worst, graze someone other than a very small person.
If you were to lift a bar stool by the seat and use the legs as a weapon, as the gentleman who appears to have thrown it did, it is neither effective as a jabbing, swinging or throwing weapon because, due to the distribution of the weight, you really can't get too much speed behind your swing.
If one absolutely must attack a standing opponent with a bar stool, and that opponent has reason to believe an attack may be coming, that guy probably attempted to do so in the most effective way, throwing it legs first (from the target's perspective) and hoping to maybe catch the target with some part of the metal, or alternatively, to distract the target (who will attempt to dodge or block the bar stool) and then rush them when they are so distracted.
Other than a very lucky shot (such as to the eye) the only way a bar stool could be a terribly effective weapon is against an opponent who has already fallen. At that point, a bar stool could be picked up much in the fashion that it would be if all you wanted to do was move it, hoist as high as reasonable into the air, and then the legs brought down into the most vulnerable area of the target possible. Even then, that would probably serve as a distraction more than anything if the opponent is ready for the attack, with the real objective being a follow up kick to the side of the head or abdomen/ribs.
Vultures can't be choosers.