A pair of liberal political action committees have launched a $5.4 million national ad buy hitting back at Donald Trump for his treatment of Gold Star mothers.

Trump last week sparred with the Khizr and Ghazala Khan, whose son was an Army captain who died in Iraq. Trump received criticism for his comments about Ghazala Khan, who stood beside her husband onstage at the Democratic National Convention as he talked about losing their son.

"Maybe she wasn't allowed to have anything to say, you tell me," Trump said.

The new ad, launched Sunday by VoteVets and Priorities USA, features another Gold Star mother, Michelle DeFord, who also lost her son, Sgt. David Johnson, in Iraq.

"When I saw Donald Trump attack another Gold Star mother, I felt such a sense of outrage. I would like to tell Donald Trump what it feels like, the sense of emptiness that only losing a child can bring. Those people should be honored and treated with kindness for the rest of their lives, and I don't think that Donald Trump will ever understand that," DeFord said in the ad.

She also talked about her experience when three soldiers showed up at her door to deliver the news that her son was dead.

"The sound of their boots as they came up those stairs will stay with me for the rest of my life ... it's a fate I would not wish on anybody," she said.

The ad will be backed by a $5.4 million buy in Florida, North Carolina, Ohio, Iowa, Nevada, Pennsylvania, New Hampshire and Colorado, as well as nationally on MSNBC, CNN, Fox and the "Today" show, according to a press release.

Last week, VoteVets also organized an open letter from Gold Star families to Trump, demanding that he apologize to the Khan family.

Paul Manafort, Trump's campaign manager, said that while Trump had not apologized, he had already "paid his respect" to the family.