President Donald Trump challenged the account of a Democratic Congresswoman, who said that he told the widow of a soldier killed in an ambush in Niger that he “knew what he signed up for.”

“Democrat Congresswoman totally fabricated what I said to the wife of a soldier who died in action (and I have proof),” Trump wrote on Twitter on Wednesday. “Sad!”

Rep. Frederica Wilson of Florida told reporters that Trump called the widow of Army Sgt. La David Johnson and was “insensitive.” She said that she heard part of the call on speakerphone when she was with the widow.

“Basically he said, ‘Well, I guess he knew what he signed up for. But I guess it still hurt.’ That’s what he said,” Wilson told CNN’s Don Lemon in an interview.

A White House aide declined to discuss the phone call with the press.

“The president’s conversations with the families of American heroes who have made the ultimate sacrifice are private,” a White House official told ABC News.