WASHINGTON -- Donald Trump and Hillary Clinton adjusted the focus of their campaigns Sunday, offering prayers and support to the victims of the mass shooting in Orlando, Fla.

The two made statements hours after a gunman opened fire inside a crowded gay nightclub early Sunday, killing dozens of people before dying in a gunfight with officers, police said. Officials said the shooter was Omar Mateen of Fort Pierce, Fla., a U.S. citizen born in New York. They said he identified himself in a 911 call from the club in which he professed allegiance to the leader of the Islamic State militant group.

Clinton pushed for gun control and reached out to a key Democratic constituency -- lesbians, gays, bisexuals and transgender people.

"The gunman attacked an LGBT nightclub during Pride Month. To the LGBT community: please know that you have millions of allies across our country. I am one of them," she said in a statement, adding a call to keep assault weapons out of the hands of "terrorists or other violent criminals."

Trump also offered words of support, but critics were upset that one of his tweets appeared to praise himself for predicting an attack: "Appreciate the congrats for being right on radical Islamic terrorism, I don't want congrats, I want toughness & vigilance. We must be smart!"

And as President Barack Obama walked to a lectern in Washington to address the nation early Sunday afternoon, Trump tweeted: "Is President Obama going to finally mention the words radical Islamic terrorism? If he doesn't he should immediately resign in disgrace!"

In his address, Obama called the tragedy an act of terror and hate. He didn't talk about religious extremists or attacks inspired by the Islamic State.

Clinton's presidential campaign announced that because of the Orlando shooting, it was postponing its first joint event with Obama, originally set for Wednesday in Green Bay, Wis.

Trump said he was changing the focus of his speech today at Saint Anselm College in New Hampshire from his case against Clinton to "this terrorist attack, immigration and national security." He also postponed a rally scheduled for today in Portsmouth, N.H.

He also noted that he "said this was going to happen" and repeated his call for Obama to resign for refusing to use the words "radical Islam." Clinton, Trump added, should drop out of the presidential race for the same reason.

Trump's first tweet of the day said: "Really bad shooting in Orlando. Police investigating possible terrorism. Many people dead and wounded."

"Horrific incident in FL. Praying for all the victims & their families. When will this stop? When will we get tough, smart & vigilant?" he later tweeted.

Tweeted Clinton: "Woke up to hear the devastating news from FL. As we wait for more information, my thoughts are with those affected by this horrific act."

Sanders speaks

Sen. Bernie Sanders, Clinton's rival for the Democratic nomination, acknowledged the tragedy Sunday, as he made a round of appearances on the Sunday talk shows. He later issued a statement of sympathy to the Florida victims.

The senator from Vermont said he would not drop out of the race and endorse Clinton until he's convinced that she's committed to fighting wealth disparity. He said he plans to meet Tuesday night with Clinton about her agenda and that he will make decisions about the future of his campaign after that.

"I simply want to get a sense of what kind of platform she will be supporting, whether she will be vigorous in standing up for working families and the middle class, moving aggressively in climate change, health care for all, making public colleges and universities tuition-free," Sanders said during an appearance on NBC's Meet the Press. "And after we have that kind of discussion, and after we can determine whether or not we are going to have a strong and progressive platform, I will be able to make other decisions."

Sanders told host Chuck Todd that he will have more than 1,900 delegates at the party's July convention, short of the 2,383 needed to secure the nomination, and that he needs to determine "what kind of agenda there will be if Secretary Clinton gets elected, if she wins the election."

During a separate TV appearance Sunday, Sanders said he thinks it is "very unlikely" that Clinton would pick him as her vice presidential running mate.

House Speaker Paul Ryan of Wisconsin also appeared on the Sunday talk shows. Ryan, who chastised Trump last week for making what Ryan called "the textbook definition of a racist comment" about a Hispanic judge, suggested that Trump is better behaved in private.

"I can't speak for his stage presence, but in private I find his temperament to be much better than what you see onstage," Ryan told George Stephanopoulos during an interview that aired Sunday on ABC's This Week.

Trump drew criticism after he contended that his stance against illegal immigration makes U.S. District Judge Gonzalo Curiel biased in fraud litigation against the defunct Trump University. Curiel was born in Indiana to Mexican immigrants.

Stephanopoulos reminded Ryan that his response to the remarks about Curiel was not the first time he had criticized Trump for his comments.

"It isn't the first time I've had to do, and it won't be the last time if this continues," Ryan said. "Hopefully, this won't continue. Hopefully, the campaign will move in a better direction so that it can be one that we can all be proud of."

Ryan added: "Look, I believe he's certainly better than Hillary Clinton. These are the choices we have."

Clinton unveils ad

Also on Sunday, Clinton's campaign unveiled its first general election ad. It will run in battleground states beginning Thursday. The campaign did not initially release information about the size and cost of the television buy.

The ad, titled "Who We Are," is narrated by Clinton.

"Today, we face a choice about who we are as a nation," Clinton begins.

The ad then cuts to Trump saying of a protester, "I'd like to punch him in the face."

The ad also shows a clip of Trump onstage, flailing his arms in an apparent attempt to mimic New York Times reporter Serge Kovaleski, who suffers from a congenital condition that restricts joint movement. It contrasts that with scenes of Clinton visiting factories, greeting diverse groups of voters and stepping off a plane as secretary of state.

She ends the one-minute spot by saying: "What kind of America do we want to be? Dangerously divided or strong and united? I believe we are always stronger together."

Two hours after the ad's unveiling, Trump responded in a tweet: "Clinton made a false ad about me where I was imitating a reporter GROVELING after he changed his story. I would NEVER mock disabled. Shame!"

In the clip, Trump was taking issue with a story Kovaleski had written when he worked for The Washington Post.

Information for this article was contributed by Laurie Kellman, Lisa Lerer and Eric Tucker of The Associated Press; by John Wagner, Vanessa Williams and Anne Gearan of The Washington Post; and by Ros Krasny and Ben Brody of Bloomberg News.

A Section on 06/13/2016