From what I gather, he didn't. He joined ~~a bunch of dipshits~~ the so-called DNR's militia. It's still a quesion how he got there in the first place, as it would require him to transit through Russia, which in turn would require a Russian visa, which isn't that easy to get and immigration is one of few things that Russia actually cares and is very strict about. And after all that, hesomehow had to illegally cross the Ukrainian border... Some hefty bribes took place, no doubt about it.

By the way, a thing to note is that Russian police is infamous for making up cases, and also for beating and torturing out testimonies for something that people didn't do. The convicts and their families now deny allegations and claim the case was fabricated. But, at the same time, it is extremely rare for an entire group of closely connected people to be arrested under such false premises. Just wanted to point that out so there is no double standard of accusing Russia of lying about everything, but then just taking some random statement at face value.