For starters you're already too far ahead of yourself. This is pending going to a grand jury but regardless of how it turns out eventually (and this case is a good deal more muddled with the dearth of released evidence, see the thread in the Pub section) it's certainly not been declared a murder yet.
As to your specific premise of what may come of this and gun laws there'll be the expected bleating from the usual suspects but it's unlikely to change anything. Change what? SYG?
The thing many people don't understand about SYG is it's not some cart blanche reason to start shooting everything. In fact some places use a phrase that might be more accurate; no duty to retreat. The reason for this is that, under the old way of looking at things, people that were universally acknowledged to have been at risk could still find themselves having to defend themselves for, well, defending themselves. Literally where the would be victim becomes the bad guy and the poor, misunderstood guy that was only wanting to ask the time (but happened to be wearing a ski mask and carrying a machete) was the victim. Hell, everyone could even agree that the shooter was likely in danger but, in their opinion, (not that their sorry butts were on the line) the shooter could have tried harder to get away. Do you really want the benefit of the doubt to always be with the attacker? I surely don't.
Again, saying you "were scared" and "standing your ground" is not sufficient to shoot somebody under any state's interpretation of Castle Doctrine. If there wasn't an identifiable threat that would legally be considered reasonable to explain one's use of deadly force SYG isn't going to save you. If you were to argue it muddies up the "grey areas" then, as I've stated above, I'd rather it muddy things up on the side of the guy claiming SD than the guy that everybody could know from the outset was the bad guy but still ended up being treated as the victim.
YMMV
