I discount it as a "true crime", it wasn't someone using his weapon to shoot someone with malice, it was a criminally negligent accident. E.g. if you bundled someone of the same age into a running car and let them have at it on your own property we wouldn't say that had anything to do with driver's licenses, if the vehicle was properly registered with up to date license plates/tags, etc.

Heck, a Micro-Uzi is essentially a big handgun, you should never give a handgun to someone that young without intense training and supervision. I started shooting long guns in kindergarten but was a teen before my father started me on handguns (other more handgun oriented parents have started their children on handguns earlier; Massad Ayoob's daughter was winning competitions as some insane age like 7 or 9).

And that's 100,000 over decades; the law dates back to FDR's first year or so in power and the number was frozen by another law in 1986.