Much like Menudo, the lineup has changed considerably over the years. The original ArchDuke was indeed assassinated by Gavrillo Princep (who pleaded, in his defense, that he was only obeying the Archduke's imperative to 'Take Me Out". After all, he had told the Serbs "I'm your villain" and also that he was "Evil and a Heathen".
Well, Eleanor (Eleanor Roosevelt) did indeed put her boots on, and with Right Thoughts, Right Words, Right Action, she helped the group to leave the dark of the matinee, consoling the bereaved bandmates by reminding them that "you could have it so much better".
For a while it looked like they were outsiders who would leave together and fade away. Many critics thought that Franz Ferdinand was the fallen. But then they did dream again, saying "No you girls", this is "what she came for". Now, with the Universe expanded, they stand on the horizon.
He didn't die at all, he was simply complicit in an Austro-Hungarian plot to invade Serbia. However years later he expressed remorse and contrition at his part in WW1 which he believed to have ultimately influenced the other horrors of the 20th century. Unable to adequately express his sorrow in prose, he ultimately turned to song:
The stab of stiletto
On a silent night
Stalin smiles
Hitler laughs
Churchill claps
Mao Tse-Tung
On the back
Source: Walk Away, Franz Ferdinand
It wasn't him, but rather a double. As described in the song All for you, Sophia, the B-side to the 2004 hit single Take Me Out, it was a plot to kill of a double so Franz Ferdinand could escape his responsibilities and life a more peaceful, private life with his wife Sophie. Note how he uses 'me' ironically to describe his body double, Gefreiter Reinhard Schwanenburg of the KuK Heer:
Bang, bang, Gavrilo Princip
Bang, bang, shoot me Gavrilo
Bang, bang, the first six are for you
Bang, bang, the seventh is for me
Bang, bang, Gavrilo Princip
Bang, bang, Europe's going to weep
All for you, all for you all for you, Sophia
Later on he details how the Black Hand were his accomplices. The primary plan was for Čabrinović's bomb to kill the unwitting double; when that filled, Franz Ferdinand (who had already disguised himself as General Oskar Potiorek) ordered the driver of the car to make a detour over the Appel Quay:
The black hand holds the gun
The devil takes his run
Urban, take the Appel Quay
It's June the twenty-eighth
The seventh was for me
This plan is also referenced in the main song of that single, Take Me Out; it references how the double himself was unaware he would be assassinated while carrying out his duties of impersonating the Archduke:
I say don't you know
You say you don't know
I say... take me out!
I fired up the /r/AskHistorians' newly-built time machine to get an answer right from the source.
FRANZ: Do you want to know a secret? Only darts of pleasure can take me out. Those outsiders - see them stand on the horizon? I can't stop feeling their evil eye on me, so though I love illumination, I sit on the dark side of the matinee. The assassins, despite this, fire at me and fade together into the night. As they walk away, the fresh strawberries I was eating fall - and I swallow, smile, and seem to die on the floor - but it takes more than a bullet for this boy to really join the fallen.
So yeah, as to your question: Franz Ferdinand was just fucking insane
That was just a publicity stunt for their single "Take Me Out". However, they exclusively promoted it on Twitter, and due to the lack of context of tweets, their intention was horribly misunderstood and led to a war.
Weren't they touring the Grateful Undead? A group of musical necromancers?