I flew to Ukraine on July 16, 2014. It was a typical flight and travelers thought they could abstract from the war in the East of Ukraine. The next day changed everything. Pro-Russian separatists shot down MH17, a passenger airplane with 298 people aboard, 80 of which were children.

This is an unspeakable crime that has shocked everybody in Ukraine and around the globe. Citizens of the Netherlands, Australia, Malaysia, the U.S.A. and many other countries had no connection to the conflict in Ukraine, but they became victims of the indiscriminate violence of the separatists.

The separatists, or more appropriately terrorists, have by now killed hundreds of people in Slovyansk, Kramatorsk, Donetsk, Luhansk and many other cities in Eastern Ukraine. And their violence and brutality has only been escalating. A few weeks ago, they shot down a military-transport airplane with 50 military personnel. A few days ago they shot down another military airplane. In early July, the terrorists boasted that they had received a sophisticated “BUK” anti-aircraft defense system. They thought that they could control the skies and must have been eager to prove it.

The available evidence is clear: the separatists firmly believed that they had shot down another military airplane and quickly claimed credit for it in social media. However, slowly they realized that the airplane was a civilian one. The terrorists reported to their Russian superiors that there was a sea of bodies, luggage, towels, etc. Human bodies and parts of the airplane were falling on roofs, into gardens and fields. The first images of the crash site (provided by Russian media who thought this was a military airplane) were horrible. One could not see photos and videos of the site without feeling the deepest shock, pain and anger.

Only with a long delay, Ukrainian and international investigators could access the site to establish the cause of the crash (few doubt it was a land-air missile launched by the terrorists), to identify victims, and to bring bodies home for burial. Reports of terrorists marauding the crash site and covering up their crime make the tragedy unbearable.

As soon as the dreadful news broke, many people in Kiev brought flowers and candles to the Dutch and Malaysian embassies. Ukrainians, who have already lost so many people in the conflict, can feel, perhaps like nobody else, sympathy for the families whose loved ones were murdered by the terrorists in such a mad and inhumane act. Could this crime against humanity have been prevented?

This would have never happened if Russia’s President Vladimir Putin did not give BUKs, tanks, guns and other arms to the terrorists. Directly or indirectly, he is responsible for MH17. Putin has joined the club of Muammar Gaddafi and Osama Bin Laden. State-sponsored terrorism is an awful crime and Putin must be held responsible for it.

This would also never have happened if the international community had not been so complacent about Putin’s aggression against Ukraine. In all likelihood, the conflict in Eastern Ukraine would not have gotten to its current state had the response of the West and other countries been firm and strong.

Instead, we have seen a stream of excuses, euphemisms, and maneuvers to postpone sanctions and avoid imposing even symbolic measures. Just a week ago, German Chancellor Angela Merkel hugged Putin at the FIFA World Cup final in Brazil. Even now, the French government is OK with selling assault Mistral-class aircarriers to Russia (but there is a ban to sell weapons to Ukraine).

Perhaps Western leaders thought that the conflict in Ukraine was far and remote, that it could take the lives of thousands and thousands of people in Ukraine but it was more important to maintain warm relations with Putin, that they could not jeopardize the profits of Western companies operating in Russia or the comforts of their voters. But they forgot that terrorism does not respect borders. It can strike anybody and anywhere.

Ukraine cannot win the war with the terrorists and their sponsors without help from the international community. If things keep evolving at the pace of the last few weeks, the cancer of terrorism in Eastern Ukraine will spread to other parts of the world. One cannot predict when or where the state sponsoring terrorism will design, support or encourage the next round of massive violence. The time has come for the international community to show leadership and put together a united front to stop this evil. It could not be any more black and white than it is now.