As the biggest fiasco in Oscars history unfolded, photographer Andrew H. Walker hovered in the wings offstage, his camera trained on Faye Dunaway and Warren Beatty as they prepared to announce the winner of cinema’s grandest prize: the Academy Award for best picture.

Except, of course, that isn’t precisely what happened. As the masses would learn later, Brian Cullinan, one of two PricewaterhouseCoopers accountants in charge of guarding and distributing the winners’ envelopes, had handed Beatty the wrong one — containing a duplicate copy of the card awarding Emma Stone the best actress prize for her role in “La La Land.” And so, moments later, Dunaway mistakenly announced “La La Land” as the winner of cinema’s top award, which rightfully belonged to “Moonlight.”

Walker, a staff photographer for Shutterstock, watched the stunning drama unfold through his camera lens. Over hours spent shooting on the red carpet and backstage, Walker had taken more than 4,000 photos, he told The Washington Post. Buried among them were a couple of throwaway images that, his photo editor later realized, were rather important: They appeared to document the defining moments that led to the unprecedented Oscars disaster.

In an unprecedented gaffe, "La La Land" was accidentally awarded the Oscar for best picture before producers realized the award actually belonged to "Moonlight." Here's how the moment played out, plus other highlights from the 2017 Academy Awards. (Nicki DeMarco/The Washington Post)

The photographs, published exclusively by Variety, reveal a striking sequence:

The first image, taken at 8:53 p.m. Pacific time, shows Warren Beatty embracing Casey Affleck, who had just won best actor. Cullinan stands behind the pair, apparently holding his cellphone and two red envelopes in his hand.

One of those envelopes would be handed to Beatty in the minutes that followed. Walker told The Washington Post that Beatty had the envelope in hand a few moments before he walked out on stage: “I took a photo of Warren Beatty looking at the monitor, and a split second before I took that photo, he was standing there with [the envelope] in his mouth, because he was tucking his shirt in,” Walker said. “I’m disappointed I didn’t get that photo.”

At 9:03 p.m., Beatty and Dunaway took the stage to present the best picture award. As they read their introductions, Emma Stone posed for photographers waiting backstage — and Cullinan snapped a pic himself. At 9:04 p.m., Walker photographed Cullinan looking at his phone, just one minute before Cullinan shared a photo of Emma Stone on Twitter. Three minutes after Cullinan’s tweet was posted, at 9:08 p.m., Dunaway mistakenly announced “La La Land” as best picture.

Walker said he was shooting with such speed and intensity that he took no notice of Cullinan in the frame at the time.

“It was definitely not a photo of [Cullinan] in particular. At the time I didn’t even know he was on his phone — I’m just surveying the scene,” Walker said of the 9:04 photo. “I had been guided to also shoot the stage staff, the stage managers, as a courtesy.”

As the cast of “La La Land” took the stage and began to deliver acceptance speeches, Walker became aware that something was wrong, he said.

“There was this weird sort of uncomfortable pause, this tension. And there was a woman standing next to me who was wearing a headset, and I don’t know who she was, but she started swearing — to herself, but pretty vehemently.”

As Walker’s photographs circulated Wednesday, new questions arose: Why was Cullinan pictured holding two envelopes, when he should have been preparing to hand over only the best picture winner? Why hadn’t the veteran accountant been focused on the task at hand as the single most important moment of the ceremony approached, as opposed to looking at his phone? And why hadn’t the two accountants, both of whom are charged with memorizing every winner, acted immediately when they heard Dunaway announce the wrong film?

The worst-case scenario was oddly foreshadowed by Cullinan in an interview with the Huffington Post days before the show. Cullinan and his ballot co-leader, Martha Ruiz, were asked what would happen if the wrong winner were to be announced by mistake. The pair said they didn’t know what the precise protocol would be, as such a calamity was entirely unprecedented.

“We would make sure that the correct person was known very quickly,” Cullinan said. “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.”

He added: “It’s so unlikely.”

Despite the barrage of criticism, jokes and “never tweet” quips circulating about Cullinan, Walker said the accountant seemed like a polished professional.

“The impression that I got about him and a couple of other people who were running the stage area there, my impression of them was just that they were very capable people,” he said. “I was flabbergasted at the amount of moving pieces that have to go into producing this show.”

But, for Cullinan and Ruiz, it would be their final year as part of the process. On Wednesday, Academy President Cheryl Boone Isaacs told the Associated Press that the two accountants would not be invited back to the Oscars.

See photos of the Oscars: The winners, presenters and performers of 2017

US director Barry Jenkins (C) celebrates on stage with producer Adele Romanski after "Moonlight" won the Best Film award at the 89th Oscars on February 26, 2017 in Hollywood, California. / AFP PHOTO / Mark RALSTONMARK RALSTON/AFP/Getty Images (Mark Ralston/AFP/Getty Images)