He crossed the border illegally and was carrying a firearm with him. Maybe it's ok in the USA to cross the border illegally carrying a firearm with you, but I assure you it's not legal in all the other countries in the world and penalty would be very severe.
Wait, he was carrying what?
Did it not occur to him that this might be a bad idea?
> Maybe it's ok in the USA to cross the border illegally carrying a firearm
By definition anything illegal is illegal, and no, you cannot bring a firearm across the border into the USA without a paperwork process.