Man, I hate that. Not knowing how it started has to make it worse.
Short of finding accelerants, the cause of fires like you had can really be hard to lock down because the fire destroys the evidence. I'm not even sure game camera pics, unless they showed the actual event, would legally prove anything other than trespassing. Now having said that, if you get a pic of a guy crawling under your fence at 3am, and a fire started right after that, any local law enforcement or fire marshal should jump on that evidence, and at least have a very solid suspect. I'm not sure how Kansas handles potential arson fires, but here, a public safety injury of any type escalates the penalty, and effort put in to determine the cause.
You've pretty much covered all the potential causes, and I would also guess it's arson. It's just that it can be really hard to prove.
Last edited by FireIsHot; 11/30/21 10:42 AM. Reason: ADD