Unless I am missing something, what makes you think they won't blame guns? What is so different about this case that they wouldn't try to blame guns? They would just use the same line that if the kids couldn't get access to a gun there would be no shooting...
Because none of the kids in the shooting:
are old enough to legally own guns and therefore
never submitted to a background check,
never took any safety courses that might have been required in conjunction with a gun purchase,
certainly didn't have a permit to buy,
no registration, and
no concealed carry permits.
Even if you toss out the fact that murder is a crime, look at all the laws they broke.
No new laws could have prevented what happened. Criminals break laws, and they have no problem finding their way to guns.
The problem in THIS story is their gang affiliation. I'd bet they got the guns from other gang members. Since black-on-black crime and gang violence are all but ignored by the anti-gun supporters, they will turn a blind eye and focus on the church shooting.