There was a post a day or two ago on FR where a polish pilot described that this pilot had only 350 hours of experience and the navigator was straight out of school. This person also described in detail the mistakes the pilot made in approaching this landing. As to the shots, since there were no survivors, I would think it was between police and looters, or looters between themselves.
http://www.freerepublic.com/focus/f-news/2497468/posts
i think that was debunked a Russian propaganda.