So, what was the assassination of Archduke Franz Ferdinand?
Well, in 1914, he was visiting Bosnia attending military exercises, and on the day before he planned to leave, he was assassinated
By who, and how?
On the day he was killed, there was first a failed attempt where a group called the Young Bosnians threw grenades at him while he was going to the town hall, but missed. After the meeting at the town hall, he was driving to the hospital when the car took a wrong turn, and a man named Princep was waiting for them in an alley. He promptly shot both Ferdinand and his Wife, killing them instantly.
And what was the aftermath?
The aftermath of this event was that, by means of all the different alliances in Europe, WWI began.