It didn't look like an active shooter to me either. No one was actively shooting.
I've been a Resource Officer in a high school for the past nine years and that looks more like a barricaded subject drill than an active shooter, but they can change from one to the other in a flash. From the perspective of the camera, we can't tell if he has students behind the door with him, or if he's alone, but they're talking about getting him something to drink, so it looks like the negotiators are trying to establish rapport.
Your observations are right on. I would have rigged a rope to the door handles to enable the others to pop the doors open.
That's assuming you had a rope to rig. How many folks carry rope with them every day? Also notice, these are uniformed cops. I'm sure that the high-speed, low-drag SWAT boys are on the way with all manner of neat toys.
At that stage of the scenario, it's the negotiators job to bore him to the point where he surrenders out of sheer mind-numbing frustration.