When Chris Rock stepped out onto the stage of the Dolby Theatre at 7:25 p.m. PST on Sunday night to present the best documentary feature Oscar — the 16th award presentation of the night if you were watching on TV, or 18th if you had been in attendance for the hour before the live telecast, when several were handed out and pre-taped — there was no reason to anticipate any problems.

Rock’s rehearsal on Saturday in front of Academy officials and his friend, telecast producer Will Packer, had gone smoothly.

And on Sunday night, with just 6 Oscars still to be handed out, the end was in sight.

Then, of course, came Rock’s joke about Jada Pinkett Smith — which was not in the script and not part of Rock’s routine at his rehearsal — which enraged Will Smith followed by the slap seen and heard all over the world.

So here is what was going on backstage, when all hell broke loose at the Oscars, according to various sources in the green room at the time.

“There were tons of people there,” says one, who remembers spotting Serena Williams and Venus Williams, and numerous A-listers waiting to present upcoming awards including Jake Gyllenhaal, Zoe Kravitz, Kevin Costner, Anthony Hopkins and the trio who would later present Smith with his best actor Oscar, Samuel L. Jackson, Uma Thurman and John Travolta.

Also present was a cadre of top-tier publicists including Smith’s own longtime rep, Meredith O’Sullivan Wasson.

Some were paying more attention to the action on the three TVs in the room, but as the Smith incident unfolded, according to another source, “It went very quiet.” Then, says another, “Everyone was like, ‘What the fuck is happening?! Did that just happen?! Oh my God!’ People were gasping.”

People who present awards generally return to the green room, but Rock did not do so after the best documentary Oscar presentation to Questlove for Summer of Soul — which most in the audience and backstage barely remember, as they were still stunned.

Smith returned to his seat after the altercation.

Rock’s manager, Jason Weinberg, sat stunned, and then was asked to go speak with the Los Angeles Police Department. (Rock ultimately declined to press charges against Smith.)

Once the show went to commercial break, the Academy’s outgoing CEO Dawn Hudson and president David Rubin, accompanied by the Academy’s press spokesperson, hustled backstage, looking as serious, walked very, very fast into a private room with Meredith.

Hudson and Rubin never returned to their seats in the audience, and Wasson spent the next commercial breaks commuting between the backstage area and Smith’s seat, where she conferred with him as he held on to a hand of Pinkett Smith, who seemed to be speaking with a rep of her own.

During the first commercial break after the incident, Smith went into a corner of the room with Denzel Washington and Tyler Perry, who consoled him and advised to brush the incident off his shoulders, each literally making the physical gesture on a different shoulder of Smith’s.

As Smith returned to his front row seat, he was hugged by Bradley Cooper, and then headed back to his seat, wiping his eyes with a tissue along the way.

Several celebs including Tiffany Haddish tried to approach the Smiths, but quickly realized that it was not an opportune time to do so.