Images today of a drone attack on a russian aircraft in a pace deep inside russia. it happened over the weekend. it was the first of two strikes inside russia over a three-day period, aimed at supersonic long-range bombers. military institutes analyst at the institute for the study of war say neither one is likely to inflict significant damage damage on russia s air support already but may it is also one of the objectives of a group of elite snappers in ukraine. who gave our nick paton walsh and exclusive look at our mission on the frontlines. they have never seen and heard fire only once. their targets just drop. ukraine s elite sniper unit from the security services, the sbu are usually invisible. like the u.s. delta force, chosen for fitness and intelligence, but unlike delta, fighting for their homeland and survival for nearly 18 months. they gave cnn a rare interview