I'm not sure this guy should be held guilty.
The one who SHOULD be charged is the commander who showed up on scene, left his radio in his car, failed to take command, and spent most of the next hour or two wandering around while innocent people were killed and nobody was giving any orders. And he says he 'didn't realize he was in command' fucking bullshit dude that is your job to know that you are a part of the chain of command. When you, a command officer, shows up on scene you should establish where you fit in that chain- if someone else is in command report to them, if nobody else is then take command. That's your DUTY. You personally don't have to rush the gunman, you just have to take command of your men.
In the absence of orders, 'do nothing' became the de facto order until a border patrol team (different chain of command) showed up and said fuck you all we're ending this.
Let's charge that commander with gross negligence.
Ah yeah I know they are different. What I meant was this guy has a clear defense under Warren v. DC (namely, that he had no specific duty to save lives) and he can simply argue that in his estimation he didn't have the ability to effectively engage, whereas the Uvalde commander is clear dereliction of duty.