Actually, the Malaysian government has reserved judgement as to who shot down Mh17, something that doesn't get paid a lot of attention in the West. They've also accused the Ukraine junta of withholding evidence related to the incident. Given that the Ukrainian military has shot down civilian aircraft before by 'accident' and were operating BUK systems in the area near the crash, they should be considered a prime suspects in any serious attempt to get at the truth of what happened.
The rebels did it, by accident. They thought they had shot down another of Kiev's AN-26 transports (as they had done the previous Monday) and posted a boast to that effect on Facebook. Then they sent troops to the scene to round up any crew who might have bailed out (two bailed out the previous Monday). But they took down their boast when the troops on the ground sent back word that nobody had bailed out and the fields were strewn with dead bodies bearing foreign passports.
