Bill Clinton AP Photo/Don Ryan JOHNSTOWN, Pa. (AP) -- Hillary Clinton's top surrogates are taking aim at rival Donald Trump for criticizing the bereaved mother of a Muslim 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.

Trump appears on ABC "This Week." Screenshot/ ABC

"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."

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.

In a statement that made no mention of Trump, Hillary Clinton said she was "very moved" by Ghazala Khan's appearance.

"This is a time for all Americans to stand with the Khans and with all the families whose children have died in service to our country," she said. "Capt. Khan and his family represent the best of America and we salute them."

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.

Post-convention it has become clear the presidential race will be fought in the struggling manufacturing towns, cities and rural farming communities of the Rust Belt, as Clinton used 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.

On Saturday, Clinton made stops in rural western Pennsylvania, a largely white part of the swing state that traditionally votes Republican.

Democratic U.S. presidential candidate Hillary Clinton and U.S. Senator Tim Kaine (D-VA) react during a campaign rally at Ernst Community Cultural Center in Annandale, Virginia, U.S., July 14, 2016. REUTERS/Carlos Barria

Clinton is playing up economic opportunity, diversity and national security. Democrats hammered home those themes this week with an array of politicians, celebrities, gun-violence victims, law enforcement officers and activists of all races and sexual orientation. Their goal is to turn out the coalition of minority, female and young voters that twice elected Obama while blunting some of the expected losses among the white men drawn to Trump's message.

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," he said.

Trump has made plans to visit some of the same areas Clinton is campaigning in during her three-day bus tour through Ohio and Pennsylvania, scheduling Monday stops in Columbus and Cleveland.

The Trump campaign swaggered out of the convention weeks, feeling bullish about the bump the nominee received from his own nominating convention.

While Clinton and 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.

Clinton highlighted Trump's use of outsourcing to manufacture some of his branded products, arguing he's profited from the same foreign labor he now blames for killing U.S. jobs.

"What part of America first leads Trump to make Trump dress shirts in Bangladesh not Ashland, Pennsylvania," said Clinton. "I just find it so maddening that Trump goes around saying this and all the stuff he makes in other countries."

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Lemire reported from Denver.