It's another terrible story about MH17 being shot down. As with any story the complexity is huge, who fired? Why was the plane there in the first place?
Neither the Ukranian nor Russian Governments have a record of honesty so little of what they say about the situation cuold be taken at face value.
The most salient fact is this though, the rebels have no airpower so the Ukranians have not been trying to shoot down aircraft. The Ukranians have been using airpower for groundstrikes, but as this is confirmed as a Surface to Air missle the only question has to be whether it was the rebels or russians themselves who fired.