'The aircraft was deliberately brought down' likely true - that's how Semi Active Radar SAMs work. I strongly suspect that the SAM operators thought it was a Ukranian military aircraft however. So the sentence 'The Malaysian airliner was deliberately brought down' is likely untrue.
As you suggest Capetonian, I expect there was very little reasoning done here. Shoot first, ask questions later.There are likely to be a lot more questions than they would have wished for this time however, and the SAM operators won't be the ones asking them.