The parents of Capt. Humayun Khan took the stage, saying they were "patriotic American Muslims with an undivided loyalty to our country."
His father, Khizr Khan, said Trump "consistently smears the character of Muslims," and decried Trump's call for a ban on Muslim immigration.
"Let me ask you: Have you even read the U.S. Constitution?" Khan said, then reached into his pocket and pulled out a copy of the document.
"I will gladly lend you my copy," he said.
He then called on Trump to go to Arlington National Cemetery, and look at the graves of the fallen representing various faiths, genders and ethnicities.
"You have sacrificed nothing and no one," Khan said.
Khan endorsed Hillary Clinton for president, saying "we will keep getting stronger" when she takes office.