I think it tells us two things.
1) If we restrict someone’s firearm, they’ll just use a different firearm.
This is what sets off the alarm bells on the pro gun camp. They see the left saying this: “this time we take this gun away. Next time we take the next gun away. The time after that we take that gun away.” And the end of that experiment is an England style “license to buy steak knives.” Theres always going to be another school shooting. Taking all the guns does not work, mathematically speaking.
2) These things, meaning school shootings, do not warrant our attention at all in a national sense. Three people per hour die from gunshot wounds in the US. The Santa Fe shooting was three hours worth of gun death. It’s a drop in the bucket, and it’s very counterproductive to craft policy around the drops.