A managing partner at PricewaterhouseCoopers LLP posted a celebrity photo on Twitter backstage at the Academy Awards Sunday night just minutes before he mistakenly gave an envelope to actor Warren Beatty that set off the disastrous announcement of the wrong best-picture winner.

Brian Cullinan, one of two PwC partners holding envelopes with the names of Oscar winners, tweeted “Best Actress Emma Stone backstage! #PWC” along with a photo of the actress at 9:05 p.m. Pacific time. That was approximately three minutes before Warren Beatty and Faye Dunaway walked on stage to present the award for best picture…

Mr. Cullinan deleted the tweet, apparently on Monday morning; The Wall Street Journal has seen copies of the tweet, including a version publicly accessible on Google’s servers…

Ms. Ruiz gave the best-actress envelope to presenter Leonardo DiCaprio, the knowledgeable people said, which resulted in Mr. Cullinan having the extra envelope for that category, which he inadvertently gave to Mr. Beatty. The best actress award was presented immediately before best picture.