Maybe if the whole thing was captured on video so people couldn't hide from it. That might change things. Like imagine if Sandy Hook was captured in ultra high detail, no holds barred mass slaughter of children it makes my stomach turn just thinking of the details). I feel like that would sway public opinion.
It wouldn't sway enough though. You have to realize that for the majority of gun owners in this country, their philosophy is that you can't "Put the genie back in the bottle" and they would rather be armed to prevent them and theirs from being shot than working toward a society where that isn't needed. Not only that but people's attention span in this day and age is so small. What happened today was tragic, but sadly it will be forgotten by the rest of the country in a week, once the next celebrity does something stupid or Trump holds another press conference.
The only way gun laws will change in this country is if this country changes because of: Civil War and a new government created, Invasion and subjugation by a foreign country, Aliens.
Probably gonna be aliens at this rate.