What happened at the Oscars is unprecedented.

The night’s biggest award — Best Picture — was handed to the wrong film, presumed frontrunner La La Land, because presenters Warren Beatty and Faye Dunaway were given the wrong envelope. It bore the name of La La Land’s Emma Stone, who had won Best Actress moments before.

The three credited producers for La La Land were almost through their triumphant speeches — indeed, the third, Fred Berger, was in the middle of speaking — when producer Jordan Horowitz was forced to take the microphone and say the film had lost to Moonlight.

Essentially everybody involved appeared to believe, initially, that it was a joke, from the moment that Beatty — clearly flummoxed by having an envelope that read “Emma Stone” — tried to make sense of what had happened, only to have the crowd (and his co-presenter Dunaway) think he was unnecessarily prolonging the announcement, to the moment when Berger said, “By the way, we lost.”

PricewaterhouseCoopers, the accounting firm that counts the Oscar ballots, issued a statement taking the blame for the mix-up:

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.

On Monday, it further clarified the situation in another statement:

PwC takes full responsibility for the series of mistakes and breaches of established protocols during last night’s Oscars. PwC Partner Brian Cullinan mistakenly handed the back-up envelope for Actress in a Leading Role instead of the envelope for Best Picture to presenters Warren Beatty and Faye Dunaway. Once the error occurred, protocols for correcting it were not followed through quickly enough by Mr. Cullinan or his partner.

Variety has much more on the mix-up.

In the moment, though, it was chaos. It’s never happened in the 89-year history of the Oscars (much less in the biggest category), and it seemingly disproved one of the longest-running Oscar urban legends.