That's a bit of a "whataboutery" argument, which is always pretty weak. I mean, let's not focus on children dying because its "only" 3% of 40,000 - I mean, 1200 children dying from guns annually is not that much relatively speaking so let's move along.
We could maybe have a broader discussion about where the criminals get their guns, as that seems to be a major reason for people having guns.
This foxnew article talks about it - interesting quote below I thought - basically the bad guys with guns get then from (lazy/incompetent) "good" guys with guns. If only we could regulate that you can buy as many guns as you want, providing you can prove that you can properly secure them when not in use.
" .. with regards to where guns are stolen from, the answer is easy.
“Lazy and incompetent gun owners,” he charged. “It’s literally that simple. Unsecured or improper secured firearms are one of the largest contributors to illegal guns on the street.”
Where do criminals really get their guns? | Fox News