Obviously, it will depend on the law's wording which hasn't been written yet. The minimum age to purchase a handgun from a licensed dealer is 21. They certainly can extend this to include other firearms.
Considering the age of majority here is 18, I suspect all these laws restricting activities to a higher age are unconstitutional. Someone between 18 and 21 should find an attorney who will work pro se to test this up through the Supreme Court.
The bag with contents was not the size of a human. Each of two cops easily carried it with only one hand. It probably contained weapons and ammo.
Congress constantly writes unconstitutional laws. Someone between 18 and 21 needs to pick a law that discriminates against them (there are several) and sue in court up to the SC if necessary.
This will force the country to either raise the age of majority or drop all these discriminatory laws. It's silly that we want 18 yo to join the military or law enforcement but on the flip side don't want them to have a firearm.