I think the whole situation is a bizarre example of behaviour you wouldn't expect from regular adult people. At the end of the day, you have no control over the actions of either Ryan or Don - you can only continue your life in the way you see best. If you start to feel threatened by either one of them, you reserve the right to get the authorities involved. If the situation continues in vain, you can always explain to Ryan that you value his friendship and have no intentions towards Don. It might be wise to keep other information to a minimum though so as to see how the situation plays out from there. You shouldn't have to justify any of your feelings or actions but keeping the appropriate people informed of the right info might help them be skeptical of anything they're hearing to the contrary.

I hope this situation doesn't become more major. Good luck.