It took an hour to enter the classroom where the gunman had locked himself because a commander thought no life was at risk despite multiple 911 calls.
This shows how inadvertently and with sheer carelessness the scene was handled.
It was like they were waiting for it to end as no one was bothered among 18 law enforcement officers waiting in the hallway.

I think they haven't followed what they were taught.
According to a training program, American law enforcement officers are taught that their focus should be first to stop the killing and then stop the dying. They are not supposed to waste valuable time so that something worse can happen. But what seemed to have occurred in Uvalde was the wasting of time when they were supposed to stop the carnage.
Some experts have also mentioned that officers in Uvalde were afraid of being shot.

Apologising or even sympathising would not calm the infuriated parents who suffer from profound grief as they lost their children in the shooting. Hence, undoubtedly, the lack of proper training or the irresponsibility to follow what is being taught to them.