"Just because you can doesn't mean you should" You can leave your coop there, but should you? Sigh, I'd worry about my animals. Even though I have more legal protection for my dogs than the average person, the chickens have limited protection. If someone killed them, even if intentionally, they...
Won't he be able to see them from your side- and as a Federal Agency FOIA does apply to EPA so you should be able to get their report eventually.
FOIA itself doesn't apply to the states but- each state has their version of it. http://www.foiadvocates.com/records.html
Also of interest might be...
If they placed the mothballs on the ground or where wild animals can reach them contact the Federal EPA and state Fish and Game and Natural Resources. Contaminating soil, water table, possibly other natural resouces. Massive, Huge, Enormous fines. Doesn't matter if it's private property.
Edited...
Yep. They'll never be satisfied- and that's not your problem.
Call as often as they act up. If the target practice ends up with bullets in your yard, call. Get a copy of ALL of the regulations covering your area and read up on them. Don't understand one- have the city/county explain it to you...