This photo shows Russian troops arresting Ukrainian naval officers in the Crimea. Surprisingly the solider is holding an AR-10 (or AR-15) rifle. It has a long range scope, a gas block bipod and a suppressor. The Kremlin wants plausible deniability that they are actually occupying the region. Like the rest of the troops occupying the Crimea, he has no insignia on his uniform. The use of Western-style rather than Russian weapons may be to give the Kremlin further deniability.
Thanks to Jim for the photo.