Donald Trump is taking issue with a speech at this week's Democratic National Convention by Muslim lawyer Khizr Khan, whose Army captain son was killed in action and who said on stage that Trump has “sacrificed nothing and no one" for America. But Democrats and advocates for veterans’ families say the Republican presidential nominee went too far in his response.

Khan made the comment during his tribute to his son, Humayun, who posthumously received a Bronze Star and a Purple Heart after being killed by a suicide bomber in Iraq in 2004.

As Khan spoke, his wife Ghazala, Humayun’s mother, stood silently by his side.

Trump, during an interview with ABC’s “This Week,” said: "She had nothing to say. She probably, maybe she wasn't allowed to have anything to say. You tell me."

And Trump challenged Khizr Khan’s claims about having sacrificed nothing. "I've made a lot of sacrifices,” Trump said. “I work very, very hard. I've created thousands and thousands of jobs, tens of thousands of jobs, built great structures."

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

Trump’s comments sparked immediate outrage on social media -- both because they critiqued a mourning mother and because many considered them racist and anti-Muslim.

House Speaker Paul Ryan, R-Wis., has previously raised concerns about Trump’s previous comments about Muslims.

On Saturday, Ryan spokeswoman AshLee Strong said: "The speaker has made clear many times that he rejects this idea, and himself has talked about how Muslim Americans have made the ultimate sacrifice for this country."

Hillary Clinton campaign spokeswoman Karen Finney tweeted: “Trump is truly shameless to attack the family of an American hero. Many thanks to the Khan family for your sacrifice, we stand with you.”

Clinton, the Democratic presidential nominee, later said in a statement: "I was very moved to see Ghazala Khan stand bravely and with dignity in support of her son on Thursday night. ... 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."

Rep. Ted Lieu, D-Calif., who served on active duty and is a colonel in the U.S. Air Force Reserve, criticized Trump and Ryan Saturday.

“Slandering a mom and dad who lost their son in service of our country is a new low even for Donald Trump,” Lieu said “What is more surprising is that Speaker Paul Ryan continues to stand by Donald Trump … I call upon Speaker Ryan to do what his heart has been telling him all along and withdraw his endorsement of Donald Trump."

Karen Meredith, a member of Gold Star Families, a support group for families who lost loved ones in the Iraq War, said Humayun Khan’s parents “showed great courage” by standing up in front of the Democratic convention and that for Trump “to insult their culture by saying that is why she did not speak is offensive.” 

“This is an attack on all Gold Star Families,” Meredith also said.

Trump's comments come a day after he attacked retired four-star general John Allen while holding a rally in front of military aircraft in Colorado. The Republican nominee also slammed a Colorado Springs fire marshal for capping attendance at his event.

Last week, during the Republican convention in Cleveland, Trump’s children repeatedly said their father had sacrificed to run for president, particularly in setting aside his successful business operations.

The Associated Press contributed to this report.