His job 'was to be his only focus,' source says.

Accountant Brian Cullinan was told not to use social media during the Oscars — despite tweeting a photo of Emma Stone just moments before handing Warren Beatty and Faye Dunaway the wrong envelope for Best Picture, PEOPLE has confirmed.

In the now-deleted tweet, Cullinan shared a photo of the Best Actress winner smiling while holding her award backstage. The time stamp shows it was posted at 9:05 p.m., only minutes before the Best Picture blunder occurred.

“Brian was asked not to tweet or use social media during the show,” a source tells PEOPLE. “He was fine to tweet before he arrived at the red carpet but once he was under the auspices of the Oscar night job, that was to be his only focus.”

The source continued, “Tweeting right before the Best Picture category was announced was not something that should have happened.”

The source added that it’s unclear whether the Academy will end its 83-year relationship with the accounting firm after the mix-up.

“The Academy has launched a full-scale review of its relationship with PwC, but it is very complicated,” the source said. “Vote-tallying and the Oscar night job is just one part of what PwC does with the Academy. It is too early to say how this will play out, but everyone is of course taking it very very seriously.”

Cullinan has not publicly commented or posted on his Twitter account since the blunder, although his PwC partner Martha Ruiz shared a selfie from the red carpet with Cullinan and Michael Strahan after the accounting firm took responsibility for the error.

PwC, the accounting firm that counts and delivers the winning Oscars envelopes, has publicly taken the blame for the incident in which La La Land was called as the Best Picture winner over the actual honoree, Moonlight. It confirmed that Cullinan mistakenly handed the presenters the duplicate Best Actress envelope instead of the Best Picture.

Cullinan and Martha Ruiz were the representatives from PwC tasked with figuring out the Oscar winners and bringing the sealed envelopes containing the well-guarded secrets to the awards show. Two PwC staffers previously told MarketWatch that for security, there are “two briefcases, that are identical, and we have two entire sets of winning envelopes.”

During the show, the two take their places on opposite sides of the stage, handing presenters their cards (depending on which side they enter from).

On top of admitting fault in the error, PwC also said that Cullinan and Ruiz did not follow protocol for correcting the error “quickly enough.” They only appeared onstage after multiple La La Land creators gave speeches – more than two minutes after La La Land was incorrectly named the winner.

Ahead of the show, both Ruiz and Cullinan seemed assured that no mistake of that kind would be made.

Cullinan told The Huffington Post before the ceremony that if a wrong winner were to be called, “We would make sure that the correct person was known very quickly. Whether that entails stopping the show, us walking onstage, us signaling to the stage manager — that’s really a game-time decision, if something like that were to happen. ”