I'm not sure what this has to do with the topic at hand.
... a young man exercising his rights and trying to prevent further damage and looting?
The kid would have a much stronger legal leg to stand on if he was actually defending the home or business of a family member. Otherwise, may just be a knucklehead who has spent too much time playing video games.
Do you have a problem with police or FBI agents crossing state lines?
In many cases, yes. I've said for years, in fact, that most of the crimes investigated by the FBI shouldn't even be Federal crimes.
I'm not sure what this has to do with the topic at hand.
I don't know if you are a little slow today, or you are just playing rhetorical games. In case it is the former, you wrote:
"You don’t cross a state line to travel to a riot zone with an AR-15 when you’re 17 years old."
Which surely suggests that you think that a 17 year old is too young to be traveling anywhere to a "riot zone" or some other dangerous place.
But that opinion of yours is not what our nation holds as a general principle. We send 17 year olds across the world to war zones to fight against determined enemies.
So presumably you are against 17 year olds serving in the military. How old do you think you should be before you are old enough to defend our nation?
One's legal rights don't require that you stay home. If you are attacked by a mob, and in reasonable fear for your life, which seems to be the case here, then the use of deadly force is justified.