UPDATE with PricewaterhouseCoopers statement: The Best Picture gaffe that marred tonight’s Oscar broadcast was caused by a doppelganger Best Actress envelope mistaken for the night’s final prize, which caused the unprecedented screw-up that temporarily bestowed the top trophy to La La Land instead of rightful winner Moonlight. Accounting firm PricewaterhouseCoopers confirmed just now that the fault was theirs:

We sincerely apologize to Moonlight, La La Land, Warren Beatty, Faye Dunaway, and Oscar viewers for the error that was made during the award announcement for Best Picture. The presenters had mistakenly been given the wrong category envelope and when discovered, was immediately corrected. We are currently investigating how this could have happened, and deeply regret that this occurred. We appreciate the grace with which the nominees, the Academy, ABC, and Jimmy Kimmel handled the situation.

The scandalous ending was the topic of conversation at the Governors Ball and other parties. Nearly everyone involved or who was in proximity has been saying that presenters Beatty and Dunaway were simply given the wrong envelope.

Beatty seemed to detect something was amiss; he was slow to call out the Best Picture winner and finally showed it to Dunaway, who saw the La La Land title and announced it.

Berry Jenkins Jordan Horowitz Oscars
“Moonlight” director Barry Jenkins, left, and “La La Land” producer Jordan Horowitz at the Governors Ball.
Pete Hammond/Deadline

La La Land producer Jordan Horowitz, who stopped the revelry to announce that in fact Moonlight was the winner, told our Pete Hammond that he was given the Best Picture envelope by a stagehand, this as fellow producer Marc Platt had given his portion of the acceptance speech. That slip clearly named Moonlight Best Picture, and Horowitz saw that Beatty held a different slip in a different envelope that had “lead actress” on it. This led to the shocking turn of events.

The question is: How could such a thing happen? And, despite the accounting firm’s claim that the mistake was quickly rectified, how is it possible that the La La Land producers not only made the triumphant walk to the stage, but Platt finished his round of thank yous, and Horowitz began speaking, before the mistake was addressed? Sources said that one of those accountants apparently told a stage manager, who handed the correct slip to Horowitz.

Jordan Horowitz, Warren Beatty, Jimmy Kimmel Oscar
Associated Press

Why was it incumbent on this producer, who just had his dreams dashed on a global stage, to announce the real winner? And why didn’t Beatty bring things to a screeching halt and insist that Kimmel or one of the show’s producers take a look at what clearly was a bogus winner card? There is clearly blame to go around, but the scrutiny will be placed on PricewaterhouseCoopers, the accounting firm that tallies the votes and keeps them secret until they can be revealed at the Dolby Theatre.

According to a pre-Oscar article on Forbes.com, there is strict protocol designed to prevent gaffes. Only two partners in the firm, Martha Ruiz and Brian Cullinan, know the winners beforehand. Each carries a briefcase with a duplicate set of the 24 winners, and they stand on either side of the stage to be able to hand winning slips to presenters, depending on which side of the stage they approach from. Best Actress winner Emma Stone said tonight that she still has her winning slip, and Beatty and Kimmel said the Best Picture winner was read from a duplicate of her prize. So the Academy and the accounting firm will have to answer how a system designed to be foolproof could have led to the worst possible screw-up, one that marred an otherwise stellar night for Hollywood.

Were both of Stone’s winners slips mistakenly placed in the one briefcase? We won’t have all the answers until tomorrow — the Academy is still trying to definitively ascertain what happened, and unlike PwC hasn’t released an official statement. But it seems likely that the prestigious accounting firm will be the ones facing an audit.