To elaborate (earlier, I was too stunned to go on at greater length):
I think this moment is akin to the Saturday Night Massacre during Watergate -- a scandal has already been growing for months, but this causes it to metastasize. The speechlessness and shock from the TV pundits was amazing to watch -- Trump was, to begin with, incoherent (answering questions about Russian interference with nonsense about Hilary's server), and finally close to treasonous, taking Putin's word over that of the unanimous conclusion of his own intelligence community. Mueller'sindictments last Friday had already upped the ante substantially, but this puts us into what Bill Kristol (Bill Kristol!) labeled a crisis moment.
I'm not saying this means Trump is gone in the short term. Nixon survived almost ten months post the Saturday Night Massacre. But, from the time of the Massacre onward, there was a presumption of guilt against Nixon among a majority of the population (and, though they were careful not to articulate it, the press), and it made his eventual departure a matter of when rather than if. I think we're in the same place today.
I also think it could play out a lot uglier than Watergate. Trump's supporters have been listening to the equivalent of Radio Rwanda for decades now in Fox News and right-wing radio, and many of them will deny reality to their graves. And, unhappily, many of those people have a good number of guns. I fear for the next couple of years.