...I don't have much: it is a tragedy. There'll not be much disagreement with that, all across the political spectrum.
I will point out that a 16-year-old in unsupervised possession of a firearm is illegal in Ohio. It's illegal under both state and Federal law for someone that age to buy a gun; it's illegal to sell a gun to them and it's illegal to have it in a school. It's illegal to shoot people who are not presenting a threat and Ohio even has very specific laws about unsafe discharge of a gun on school property.
Seems unlikely that one more law would have prevented this terrible crime. You do have to wonder, though, if one more real friend might have: the shooter is being described as a "quiet loner," as so many are. Social isolation seems to be a frequent precursor ingredient in this kind of behavior. --Smile at a stranger and say "Hi" today; it might not help but it is unlikely to hurt.
2 months ago