The demand was that Austrian officials should take part in the investigation into the assassination and in the hunting down and prosecution of the ring-leaders on Serbian territory, which would have infringed Serbia's state sovereignty. Serbia was required to react within 48 hours.
As for the Austro-Hungarian authorities participation in this investigation, the Serbian Government cannot accept it, because it would violate the Constitution and the law on criminal procedure.
The Austrians fully expected Serbia to reject these demands, allowing Austrian forces to invade Serbia and quickly defeat them before their ally and protector, Holy Mother Russia, could react militarily.
So after that, what do you think? Obviously yes.