What kind of medical treatment ending, could cause someone to die so quickly after?

Can someone survive after being taken off life support?

People tend to stop breathing and die soon after a ventilator shuts off, though some do start breathing again on their own. If he is not taking in any fluids, he will usually die within several days of a feeding tube removal, though he may survive for as long as a week or two.

He has probably been on ventilator for past several months. I doubt he did made those last statements against Trump, and recent tweets were more than likely not him.