We don't have to. It's pretty obvious a child a few countries away from home dying at the border between countries was trying to cross illegally. They didn't just get lost on the way home from school.
The borders between states is nowhere near the same as the border is between sovereign nations. We do have the right to travel. It's not just a meme from sovereign citizens. And as far as I'm aware, he was not charged with a crime for having a firearm. He was legally allowed to carry it.