So you're saying the AR -15 is especially useful to Cruz because it equalizes his abilities to kill as compared with a precision shooter?
Assuming Cruz could obtain a driver license by age 19 in Florida, and he could borrow, buy, rent or steal a motor vehicle.
He could have easily done his dirty deed, mowing down people with his motor vehicle. (Think Charlottesville, Paris, Berlin, etc)
So do we propose restricting or banning motor vehicles, so dangerous people can't get them?
We need dangerous people control, not dangerous object control.
Once police have been called to his home 20 times, do you take all of the vehicles in his vicinity, off the road?