Caring with no significant action in prevention doesn’t really signal caring. Sure, it sucks, headlines get printed for a couple of months, then people forget and move on.
To put it in the most disrespectful and sad way, it looks like more people have been on the streets for Knicks games than most (any?) school shootings of the past decades.
It's just harder to get the average joe charged up to fight a battle with anything meaningful on the line. Americans are used to living relatively cushy lives where they don't sacrifice their QOL to make the lives of their countrymen better. The closest thing to that are people in the military, and it's probably been a while since the US military is improving QOL, on average.
People will continue to be complacent on multiple fronts until it absolutely comes to a violent boil. I don't really see half measures or peaceful protests changing anything. And maybe I'm pessimistic, but I think the upcoming elections will either not change enough or be strongly manipulated to maintain the status quo.
I think your assumption of lack of caring is misplaced. The citizens clearly care, but have no power to do anything about it. Those in power are the ones that do not care or are paid not to care.