He can shoot at people because he was sold a gun and anyone who has a gun can shoot at anybody they decide. What we’re actually waiting to learn is “Will this former responsible gun owner get away with shooting at people?”.

If the answer is “yes” then other gun owners are going to do the same thing because they want to shoot at people.

If the answer is “no because he didn’t have a ‘no trespassing’ sign” then gun owners are going to buy “no trespassing” signs and then shoot at people, because they want to shoot at people.