We must await the outcome of inspections, satellite monitoring data and examination of the black box to be sure, but it seems increasingly likely a Russian-made Buk surface-to-air missile system, supplied by Moscow to pro-Russia separatist fighters in Eastern Ukraine, and perhaps even operated by Russian-trained personnel, shot down the Malaysia Airlines flight killing 298 people.
The enormity of this crime raises serious concerns and huge implications.
As the President of Ukraine Petro Poroshenko said, "This was not an 'incident', this was not a 'catastrophe', this was a terrorist act."
The US had already just imposed further tougher sanctions on Russia for continuing to provide weapons to the Russian separatist rebels. Although the EU sanctions regime is less tough, reflecting ongoing dependence of several states on Gazprom supplies, I think there will now be public pressure on governments here, in the Netherlands and elsewhere to do much more. But the problem we face is that Russia, despite its mounting economic problems and capital flight, still holds several cards. It is a permanent member of the Security Council, able and willing to use its veto to protect its position in Syria, Iran and elsewhere. And the British financial system, London property markets and Conservative party are still very happy to take money from Russian oligarchs.
Putin knows this very well but he also knows that Russia cannot afford to be regarded as a terrorist-backing rogue state. He must swiftly act to rein in the extremists in Donetsk and cooperate in an international investigation of this war crime. He should also work rapidly to end the conflict with Ukraine. But he probably will not do this because his whole strategy in Ukraine was based on pressure to keep it under Russian domination and prevent Ukraine associating with western countries through the EU. That is why he occupied and annexed Crimea, tearing up an agreement signed by Russia in Budapest in 1994, and why he has armed and supported separatist extremists in Ukraine.
If Putin does not change course, we face not just a new cold war but the danger of intensified armed conflict in parts of the former Soviet Union. The forthcoming NATO summit in Wales in September will be the most important for a generation. Is Europe prepared to act more effectively to stand up against terrorism or do we just want business as usual with Putin and his oligarchs?
Mike Gapes is Labour MP for Ilford South and is a member of the foreign affairs select committee