The Academy of Motion Picture Arts and Sciences denounced Will Smith's actions and opened an inquiry into the incident.

Mr. Smith apologized to Mr. Rock on Monday evening, after he accepted the award for best actor.

He said in the statement that his actions were not indicative of the man he wanted to be.

His apology came as the academy, a major Hollywood union and others criticized his actions, which stunned viewers around the world and overshadowed the Oscars.

The film organization condemned the actions of Mr. Smith at last night's show.

The academy made a statement after the meeting. A document on standards of conduct is accompanied by a list of unacceptable behavior. It prohibits physical contact that is unwanted and inappropriate in the situation, as well as coercive sexual attention.

Disciplinary action could include suspension of membership or expulsion from membership.

When Harvey Weinstein was kicked out of the Academy, it was not known that he had been expelled before. After adopting a code of conduct for members, the organization expelled Bill Cosby, who had been convicted of sexual assault, and Roman Polanski, who had fled the country years earlier while awaiting sentencing for statutory rape.

The Screen Actors Guild-American Federation of Television and Radio Artists, the union representing thousands of people who work in film, television and radio, did not comment on the incident.

The union condemns violence or physical abuse in the workplace.

The incident began after Mr. Rock made a joke about Jada Pinkett Smith's hair. After Mr. Smith hit Mr. Rock on the stage, viewers wondered if the blow was scripted.

Jada Pinkett Smith and Will Smith in the audience at the ceremony.
ImageJada Pinkett Smith and Will Smith in the audience at the ceremony.
Jada Pinkett Smith and Will Smith in the audience at the ceremony.Credit...Ruth Fremson/The New York Times

There were serious discussions about removing Mr. Smith from the theater, according to two industry officials who were granted anonymity to describe internal deliberations. The best actor award, which Mr. Smith was heavily favored to win, was fast approaching and stakeholders had differing opinions on how to proceed. The other said there was concern about disrupting the live broadcast.

The actor spoke with Mr. Smith during a commercial break. Mr. Smith was the winner of the best actor. Mr. Smith said that Mr. Washington had told him to be careful. That's when the devil comes for you, Mr. Smith said, but not to Mr. Rock.

Mr. Smith said that Richard Williams was a fierce defender of his family.

He received a standing applause.

Mr. Smith apologized to the Academy, the show, and his wife because of the joke.

He said that his behavior has stained what has been a beautiful journey for all of us.

The awards were overshadowed by the incident. On ABC's Good Morning America on Monday, George Stephanopoulos described it as "something we have never seen before."

The powers-that-be at the Oscars had been intent on not repeating last year's record-low ratings, putting a series of changes in place they had hoped would draw more viewers. They didn't anticipate that the broadcast would become must-see television.

Will Packer, one of the show's producers, said after the show that it wouldn't be boring. He said that it was a very painful moment for him. On many levels.

The show drew a bigger audience than last year, but interest remained depressed. According to ABC, the awards show attracted over 15 million viewers, a 56 percent improvement over the previous year. Sunday night's show was the second least watched Oscars ever.

Comedians who tell offensive jokes for a living raised concerns about the precedent Smith had set.

It's a bad practice to walk up onstage and physically assault a comedian.

Jimmy Kimmel, the comedian and talk show host who had been the last person to host the Oscars, said that he felt bad for the show's hosts.

I feel bad for Will Smith, because I think he let his emotions get the better of him, and this should have been one of the great nights of his life. Was there anyone who didn't like Will Smith? Like no one? He doesn't have a single comedian friend.

On The View on Monday, Goldberg said she didn't think Smith's award would be revoked.

She said there would be consequences, and that they wouldn't take the Oscar from him.

Mr. Rock after the incident with Mr. Smith, seated in front of him. 
ImageMr. Rock after the incident with Mr. Smith, seated in front of him. 
Mr. Rock after the incident with Mr. Smith, seated in front of him. Credit...Ruth Fremson/The New York Times

The Los Angeles Police Department said it was aware of an incident at the Oscars in which one individual slapped another. The person who was involved refused to file a police report.

The police said they would complete an investigative report if the involved party wanted one.

Marshall Herskovitz, a former president of the Producers Guild of America, called for Mr. Smith to be disciplined.

Two industry officials said that Mr. Rock's joke was ad-libbed.

Bruce Vilanch, a past head writer of Oscars shows who did not work on this year's show, said that everything that is in the script is checked. There is no time to vet if a comedian comes out and ad-libs something. I'm pretty sure that's what happened last night. This was not the material that was practiced.

The Smiths were teased from the Oscars stage by Mr. Rock. The Smiths boycotted the awards show in 2016 because the nominees in the four acting categories were all white, and Mr. Rock joked about it. Jada is boycotting the Oscars like I am boycotting panties. I wasn't invited.

Mr. Smith danced at a crowded party after the Oscars while holding his trophy, but he avoided questions about the incident. A publicist for Mr. Rock did not respond to requests.

Jaden Smith, one of the Smiths' children, wrote simply: "And That's How we do it."

Hollywood's reaction ranged widely. Smith's colleagues expressed sadness, confusion, disbelief, anger, and in some cases, empathy in interviews following the show. Many people ignored questions about the episode.

The actor said that stand-up comics are good at handling hecklers.

One top studio executive, who declined to speak on the record, voiced disappointment in Smith and in the fact that the audience in the theater gave him a standing ovation.

The way casual violence was normalized tonight by a collective national audience will have consequences that we can't even comprehend in the moment, according to Janai Nelson, the president of the NAACP Legal Defense and Education Fund.

The author Frederick Joseph said that many people took on Will Smith and Chris Rock because their partners were not Black women. We don't know what Jada has gone through.

Tiffany Haddish, who starred in Girls Trip with Ms. Pinkett Smith, said in an interview that she appreciated seeing Mr. Smith protect his wife.

It was the most beautiful thing I've ever seen, but for Ms. Haddish, it made her believe that there was more.

The day after, the prevailing reaction was mostly disbelief.

Ryan said on his morning show that he was not sure where the backlash would end up.

He reported from Los Angeles. Julia Jacobs and Matt Stevens were in New York. Dave and Tiffany were involved in reporting.