What event sparked the beginning of World War 1?

In Sarajevo on June 28 1914 the Archduke Franz Ferdinand of Austria and his wife

Sophie the Duchess of Huhenberg were riding in an open car traveling down the street,when

their driver made a wrong turn and 19 year old Serbian Gavrilo Princip assassinated him and his wife.Because Archduke Ferdinand was the heir to the Astro-Hungarian throne this was a big deal.Then Astro-Hungary made demands against the Kindom of Serbia very few of which were met. The Kingdom of Serbia felt threatened and mobalized its army.Astro-Hungary then declares war on the Kingdom of Serbia only.WW1 has started, with the Allies:France,the UK(and all its colonies),Russia,Belgium,Serbia, Italy, Romania,Japan,and the US.The Axis powers otherwise known as the Central powers were:Astro-Hungary, Germany,Bulgaria,

and,the Ottoman Empire(Turkey).