Schell is not. Standing down no matter what is a civilian's order, and the new police chief was following orders. This has Schell's bloody fingerprints all over it. That's what we pay police for, and they take pride in it. If it's too dangerous an action for riot cops to save an obviously threatened life, it's too dangerous for anyone to be there, and the crowd must be dispersed.
Apologists cite the difficulty of pleasing everyone.
You go in too early, people criticize you. You go in too late, people criticize you. If someone's dying, act. It's really not rocket science. It wasn't Schell's fault, obviously, that those violent kids wanted to act out on a mass scale.