Vladimir Putin came to power in 1999-2000 in large part due to his willingness to use brutal, indiscriminate force against Chechen “terrorists”, causing tens of thousands of innocent casualties in Chechnya. During his more than 14 years in power, he has:

• headed a regime in which critics are often intimidated, imprisoned, and even murdered;
• armed, aided, and abetted Bashar al-Assad’s slaughter of the Syrian people;
• attacked and invaded neighboring states Estonia (via cyberwarfare) in 2007, Georgia in 2008, and Ukraine in 2014, and used economic and energy tools, including gas cutoffs in the middle of winter, to pressure them.

Now Putin appears to have the blood of 298 passengers and crew from Malaysia Air Flight 17 on his hands.

Indications suggest that the airliner flying over eastern Ukraine, territory controlled by the Russia-supported forces, was downed by a missile fired from a Buk-M1 air defense system; Russian separatist forces bragged in June about capturing such systems from a Ukrainian military base. Immediately after MH17 was hit, Igor Strelkov, a Russian citizen who has been leading the fight against Ukraine, claimed that his forces brought down what they thought was a Ukrainian military plane. On previous occasions, Strelkov (Girkin) and his Russian-backed forces have brought down several Ukrainian military planes, including two Ukrainian Su-25 jets on Wednesday. It was simply a matter of time before they risked hitting a civilian aircraft.

Putin has done absolutely nothing to rein in the forces that he unleashed, despite pleading from Western leaders. On the contrary, in the past week alone, there is indisputable evidence of Russian armored vehicles and heavy weaponry crossing the Russian border into Ukraine. Strelkov and others have visited Moscow regularly to receive support and instructions.

The entire crisis in Ukraine is the responsibility of Putin. Last fall, he pressured Ukraine’s then-President Viktor Yanukovych into abandoning deals with the European Union, setting off a wave of protests in Ukraine. In February, Putin offered Yanukovych a $15 billion bailout but only if Yanukovych brutally suppressed the protestors; more than 100 people were killed in downtown Kyiv. After Yanukovych fled Ukraine and forfeited power, Putin, terrified that such a scenario might be repeated in Russia, invaded Crimea and staged a rigged referendum that led to Russia’s annexation of the peninsula in March. Dizzy with success in Crimea, Putin decided to try his luck in the eastern parts of Ukraine, but ran into a lack of support among Ukrainians living there and resistance from reconstituted Ukrainian forces.

For months, Putin has been doing his best to destabilize Ukraine by sending in forces and arms, including tanks, and cutting off energy supplies. More than 500 people have been killed in the fighting for a separatist cause that few Ukrainians actually support.  The so-called “separatist” leaders are in most cases Russian citizens; their frequent visits to Moscow for consultations underscore how easily the conflict could have ended had Putin decided—or been forced to decide—to do so.

While there is need for a full and transparent investigation of the shootdown of MH17, Western leaders should not wait for that investigation to conclude before taking action. First, on top of the targeted sanctions announced by the U.S. on Wednesday against some key Russian enterprises, it is time for full-scale sectoral sanctions on Russia’s banking, energy, defense, mining, and technology sectors. The Europeans should follow suit, but the U.S. should be prepared to go it alone if the EU continues to drag its feet—and these measures should be announced immediately.

Second, France should announce the cancelation of the deal for the Mistral amphibious assault ships slated to be delivered to Russia this November. Not doing so is just unconscionable. Instead, Paris and other NATO capitals should provide Kyiv with serious military weaponry to enable Ukraine to defend itself.

Third, Western leaders need to adopt a different attitude toward the Russian leader. Putin runs an enormously corrupt, authoritarian regime that has as its main goal staying in power at any cost. He has caused the deaths of thousands of people, destabilized his neighbors, supported murderous like-minded tyrants elsewhere around the globe, and repeatedly violated the human rights of his own people. He may be popular among Russians these days, but that should not deter the West from pursuing a principled policy.

Placing Putin himself on the visa ban and asset freeze list would be a huge step, equivalent to a declaration of political war. But if the downing of MH17 doesn’t get people to start thinking along such lines, how many more innocent victims will it take?

Those of us who have been calling for tough sanctions for months have been warning that things could spin out of control and that, undeterred, Putin might threaten other countries in the region and beyond. The tragedy of MH17 should be a wake-up call to Western leaders to stop dragging their feet and to take decisive action now. They should stop treating Putin as a normal leader and instead treat him as the international pariah that he is.