GOP frontrunner Donald Trump referred to Sen. Elizabeth Warren as “the Indian” during a press conference on Monday.

Trump’s label came after Warren unleashed a series of tweets calling Trump a “loser.”

“Who is that, the Indian? You mean the Indian?” Trump asked a reporter who questioned him about Warren.

She claims to have Native American ancestry.

“Warren’s contention became a point of controversy during her 2012 U.S. Senate race when her Republican opponent, former Massachusetts Sen. Scott Brown, demanded proof. Warren has repeatedly defended her statements,” ABC News notes.

Trump also mocked Warren’s heritage claims during a previous interview with New York Times columnist Maureen Dowd.

“I think it’s wonderful, because the Indians can now partake in the future of the country,” Trump reportedly said to Dowd. “She’s got about as much Indian blood as I have.”