Although it is popular to blame the rebels for the shoot-down, it may have been done by the Russians themselves. By this line of reasoning, the airliner was mistaken for a Ukrainian military transport plane.
Quoting Reuters, “But Russia kept up pressure on Kiev over the cross-border shell incident. A Russian newspaper, citing a source close to the Kremlin, said on Monday that Moscow was considering the possibility of pinpoint strikes on Ukraine in retaliation.”
It’s the kind of small-scale, pushbutton atrocity we have become inured to. For why Putin does not seem touched, see “Putin, Rodeo Bull Rider.”