Thats the thing, you cant buy those versions and bring them in to California. His had high capacity magazines and no bullet button. A bullet button is a piece that makes it impossible to quickly swap out magazines, you have to stick something with a point (usually a bullet is used, hence the name) into a hole to hit a button that releases the mag. Further, you cant buy those guns legally out of state unless you are a resident of that state. Reports say that they found multiple high cap magazines in his house.
It seems minor, and in my pro-gun opinion they are fairly minor besides proper registration, but these are major fucking no nos in California.
If it were only the gun thing hed probably get them taken and a slap on the wrist fine, but this tard has issue after issue building up and those issues mixed with guns looks really bad.