Hillary Clinton's top surrogates are taking aim at rival Donald Trump for criticizing the bereaved mother of a Muslim U.S. Army captain, a comment that sparked outrage across the political spectrum on Saturday.

Democratic vice presidential nominee Tim Kaine expressed shock that the GOP nominee would attack Ghazala Khan for not speaking during her husband's address to the Democratic convention.

"He was kind of trying to turn that into some kind of ridicule," Kaine said after a campaign event in Pittsburgh. "It just demonstrates again kind of a temperamental unfitness. If you don't have any more sense of empathy than that, then I'm not sure you can learn it."

Former President Bill Clinton, who joined his wife and Kaine at the event, agreed: "I cannot conceive how you can say that about a Gold Star mother."

Lawyer Khizr Khan gave a moving tribute to their son, Humayun, who received a Bronze Star and a Purple Heart after he was killed by a suicide bomber in Iraq in 2004. During the speech, Khan's wife, Ghazala, stood silently by his side, wearing a headscarf.

"If you look at his wife, she was standing there. She had nothing to say. She probably, maybe she wasn't allowed to have anything to say. You tell me," Trump said, in an interview with ABC's "This Week."

Ghazala Khan has said she didn't speak because she's still overwhelmed by her grief and can't even look at photos of her son without crying.

Trump also disputed Khan's criticism that the billionaire businessman has "sacrificed nothing and no one" for his country.

"I've made a lot of sacrifices. I work very, very hard. I've created thousands and thousands of jobs, tens of thousands of jobs, built great structures," Trump said. He added: "Sure those are sacrifices."

Late Saturday night, Trump released a statement calling Humayun Khan "a hero," disputing Khizr Khan's characterization and attacking Clinton as unqualified to serve as commander in chief.

"While I feel deeply for the loss of his son, Mr. Khan, who has never met me, has no right to stand in front of millions of people and claim I have never read the Constitution, (which is false) and say many other inaccurate things," Trump said. "If I become president, I will make America safe again."

Trump's comments sparked immediate outrage on social media, including from Republicans, who criticized Trump both for attacking a mourning mother and because many considered them racist and anti-Muslim.

Hillary Clinton told voters gathered in a Youngstown gymnasium late Saturday: "Donald Trump is not a normal presidential candidate. Somebody who attacks everybody has something missing."

"He attacked the distinguished father of a soldier who sacrificed himself for his unit, Captain Khan," she said. "I think it is fair to say he is temperamentally unfit and unqualified."

Trump's comments about Khan came a day after he criticized retired four-star Gen. John Allen and slammed a Colorado Springs, Colorado, fire marshal for capping attendance at the event. The fire marshal, Brett Lacey, was recently honored by the city as "Civilian of the Year" for his role in helping the wounded at a 2015 mass shooting at a local Planned Parenthood.

"Our commander in chief shouldn't insult and deride our generals, retired or otherwise," Clinton told a crowd gathered Saturday on a factory floor in Johnstown, Pennsylvania. "That should really go without saying."

Trump also accused Clinton via Twitter of "trying to rig" the fall presidential debates by scheduling two of the three debates on the same night as NFL games. The schedule was set last September by a nonpartisan commission, which said the campaigns were not consulted about dates. Trump also said the NFL complained to him about the debate schedule in a letter, but the league said it sent no such letter.

On Saturday, Clinton campaigned in Pennsylvania and Ohio, using the days following her convention to try and win back some of the white working class voters that once made up a key piece of the Democratic Party's electoral coalition. Trump's anti-trade message has appealed to those voters, who feel frustrated with an economic recovery that's largely left them behind.

While Clinton and her running mate, Tim Kaine, attempted to sell their positive economic message, much of their strategy centers on undermining Trump, particularly the business record that makes up the core of his argument to voters.

At a rally in Pittsburgh, she was introduced by Mark Cuban, the Dallas Mavericks owner, technology investor and television personality who recently endorsed her.

"Leadership is not yelling and screaming and intimidating," said Cuban.

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Lemire reported from Denver.

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