When I was a reporter, I dealt with varying, even extreme differences of professionalism and competence in local police departments. (Small-town police forces tend to be, shall we say, idiosyncratic -- and often corrupt.) I learned to recognize the smell of possible police misconduct and obfuscation, and what happened in Uvalde reeks to high heaven.
The actions of this police force indicate a department that knows it is unaccountable to anyone, and I guarantee you there's more there. Since the non-profit Texas Tribune is one of the best investigative publications out there, I'm confident they'll dig it out.
One place they might start is to sue to get a copy of UPD's updated policy & procedures manual -- which insurance companies require for liability coverage (at least on paper. Insurance companies are corrupt, too).
And I'd file a FOIA lawsuit for the disciplinary records of every one of those cops. I suspect there aren't any. You know why? Because politicized police departments don't update their P&P manual for a reason: If a policy isn't in writing, you can't discipline a cop for violating it. (And police unions like it that way.)
Of course, politicians look the other way. That's the agreement. And even the good politicians are afraid of the cops, since motivated cops think nothing of digging up dirt on their perceived enemies. (As their exes can verify.)
Just another way that men with guns who see themselves as victims hold this country hostage.