If I strated a riot in AZ from MO, I believe I'd get deported to AZ, while we don't do that with all other countries, I would not mind seeing those responsible deported and tried there for this incident, and if not, held accountable here.

It would motivate him to leave without incident.

Make sure you have lots of liability insurance and focus on running a great business; the incidence of actual suits is miniscule.

That is a violation of Dodd-Frank laws with a manditory $10,000. fine and 1 year prison time per incident. 

As a PM, I text/email/call owners any time there is a big issue and send them an incident report or some kind of maintenance documentation.

The incident happened after very heavy rains in the area.To fix the problem would be 15k.

Your question has prompted me to ask around a bit to learn which communities have higher incidence of Radon.  

They do this strictly for security as they have had incidents where people were armed and resisted. 

I'm thinking that this is an isolated incident.  

Draft a little one page Release that states everything you have talked about in this thread (you're not at fault, releasing you from any and all other damages from the incident, and having him acknowledge the sections of your current lease will prevail in any new situations going forward).