Here's a video of the televised event with a second-by-second timeline:
.06-14 seconds: Beatty looks in the envelop, and realizes something is wrong (he later explains, and Price Waterhouse acknowledges, that what's in the envelope is the card announcing Emma Stone winning best actress for La La Land). He's likely looking to see if there's another announcement card - one for the best motion picture.
.14-16 seconds: Beatty turns to Faye Dunaway, hoping she might have some idea about what's going on, but she just gives him a reproachful look, thinking he's horsing around at the wrong time.
.17 seconds: Feeling the pressure, Beatty begins to announce, "And the Academy Award..." But he can't bring himself to finish, because he knows something is not right.
.20 seconds: Beatty looks down again at the card, thinking maybe he missed something.
.21-.25 seconds: Beatty says "for best picture..." He looks past Dunaway, desperately hoping, again, for some guidance from someone off-stage. Dunaway, still thinking he's joking, says "You're impossible."
.26-29 seconds: Beatty, unable to continue, because he knows something is wrong, gives the envelope to Dunaway, who barely glances at the errant card, and announces "La La Land"
So ... we still need to find out how exactly Price Waterhouse - or the people or person at Price Waterhouse - came to give Beatty the wrong envelope (Russian hacking, maybe? - I'm only joking) (mostly) (he did direct, co-write, and star in Reds). But, Warren Beatty can hold his head up, if not high, at least not too low, as someone who struggled with tens of millions of people watching him, to do the right thing, under incredible pressure.
Once upon a time, prior to the digital age, a mistake made on television and wrongly attributed left the non-culprit with little recourse, totally at the mercy of the "professional" critics who sounded off today. But also today, videos on YouTube show the truth. Beatty wasn't a villain last night - to the contrary, he was almost a hero.