All of his weapons were legal but should not be by any rational reading of the Second Amendment. Did the founders really intend to empower crazy people to kill children at school or worshipers in a church? If they did, then we should all have the right to portable nukes — for that is the logical conclusion of such an argument.
No, the Second Amendment became a cancer because lawmakers stopped making laws to match the technological advances of weaponry. They did it to appease a lobby of gunmakers. And that cowering to a single special interest shows how the cancer has spread to the democracy itself, making it nearly impossible for majority will to be exercised.