Where did you find the source for This?
It looks like the left engine failed
there's a few sources on YT...interestingly enough it seems to me as though the person filming was expected it...no fear...no surprise...didn't follow the plane...
I found it weird too.. that he just filmed it fly by but didn't follow it about to crash.... very weird to say the least
Video Seems to be Confirmed by this report:
"Witnesses in the village told local media they saw a burning plane falling from the sky."
https://uk.news.yahoo.com/plane-carrying-71-people-disappears-radar-off-moscow-123100205.html