[SCR1]

There you go, thinking it was a person buying an evil look-a-like AW at a gun show in America. This guy wouldn't bother with such low power, I suspect he has a Fullauto M16 or the like.

[Fixit]

I have to agree with SCR1 on this.

Someone willing to commit these crimes would not be worried about violating mere firearms laws regarding allowable non-NFA configurations.

The shooter's weapon could potentially be both short-barrelled & select-fire. Full auto for when the SHTF and short-barrelled for concealability.

(This post contains 100% pure speculation. Accept no substitutes.)