This was a Ukranian national, not a Russian.

Yes and the sealed indictment from 2012 was unsealed in 2014, the same year as the Russian invasion of Crimea and Eastern Ukraine, which was also the direct trigger for Ukraine switching from a non-aligned position to seeking very close cooperation from the US.

I can very easily see how home in both the narrow regional and broad national sense could have become quite risky for a number of reasons for him from 2014 on.

152mm artillery shells don't care what your passport says.