Yes and no.

It kicked off what is called the July Crisis, which was a spectacular series of diplomatic blunders by most parties involved. The Serbians falsely claimed to have warned Franz Ferdinand about the assassination plot, then backpedaled when they realized this was an admission to knowing about the conspiracy.

Montenegro caught one of the surviving conspirators, questioned him, and then ignored an Austro-Hungarian extradition request and helped him escape their own custody.

Franz Joseph, who had just lost his son, was supported by Wilhelm in basically anything he decided to do to deal with Serbia. This would have definitely meant war with Russia and France, and the German high command responded to concerns about the outcome of that by basically saying "hold me back bro."

Wilhelm was hopeful that a really belligerent attitude combined with a rapid offensive against Serbia would keep the war localized to the Balkans. Others in Germany welcomed the opportunity to attack Russia, as they feared Russian industrialization would reduce Germany's power in the coming decades. It became pretty clear to everyone involved that Germany was eager for a larger war; the Archduke's assassination and Franz Joseph's determination to deal with his problems in the Balkans provided them with an opportunity for a war against pretty much everyone they wanted to fight, and a few others added in for good measure.

Even after Ferdinand's assassination, war could very very likely have been prevented at several points if the right people had made different decisions.

People, even powerful policymakers, were quite shocked when the war broke out. Everything spiraled out of control rather quickly.