Most likely a gun deal or assassination gone bad.
Assassination gone bad.
He was supposed to provide the diversion, which he did. He was also to provide cover afterwards for their escape, which became unnecessary.
The assassination attempt on the Arab Prince went bad because the Prince wasn't there.
He had dressed up like a normal US citizen and went out on the town, so to speak.
Once the handlers realized the assassination was off, they shot him and escaped to the 33rd floor.