That, or something like it. Scalia-ed.
Supposing the scenario is true—suicide or euthanasia by morphine is believable. (He did not look well in his pictures.) I think this is easier to believe than his being secretly executed.
What the deceased’s family told the Media may be the date and time that they were requested to say. The press will dutifully announce that date and time to the world. It may not be the actual date and time of death, which presumably would be correct on his Death Certificate, which will NOT be distributed to the press and will indicate the cause of death as his cancer.
So, this would be a proof because Q provided the date and time of death in advance and the family agreed to announce his passing at that date and time.