Obviously you were using a small lightweight camera, but a single c-stand and a few sandbags is not really adequate for this sort of work. Yeah, it'll work fine 99 times out of 100. It's the 100th time that you overengineer for. Those rotary clamps sometimes fail, eg because sufficient strain and a history of overtightening causes one of the screw threads to shear, and then your arm slides right out despite the sandbag on the end. In windy environments the momentary strains are much higher than the steady one of the weight.
Had that happened in this case, the arm and the camera would have been traveling at >100mph when it hit the ground, on the busiest streets in the city. When you rig something that could put someone else at risk, rather than just what's attached to the rig, you build with the assumption that each individual component may catastrophically fail.
At the very least, you should have had a second stand farther back with an arm clamped to the near end of your working arm, plus you should have one person on each stand whose only job is to watch the stand. What you have here is OK for the height of a garden shed or the deck of a low-rise apartment building. It's absolutely not OK for the roof of a skyscraper, man.
And that's with the thing just bearing the camera load. You had the models using your load-bearing stand, which you are holding with only one hand, to steady themselves as they step up on the edge wall. They're gripping it well above your point of contact. If one of them lost it, s/he would have pulled the whole rig down, exponentially increasing the chances of the arm coming free. Or the camera coming off its mount. Or the ballast bag on the arm vaulting over the side.
Fort that matter, at the start of the video you're leaning out videotaping yourself with a camcorder that isn't visibly secured to anything and that doesn't have any gaffer's tape securing the battery to the camera. At this height anything that falls presents a deadly danger to the people in the street below. A camcorder battery is certainly heavy enough to kill someone. Sure, you're a careful guy, you've probably never dropped your camera. But even though nobody means to drop a heavy light or an expensive lens or a c-stand or a camera or a sandbag, I've seen it happen many many times in the middle of film production. Shooting without permits is one thing, disregarding well-established safety practices is quite another.
