Billionaire business tycoon Elon Musk, who was named Time’s “2021 Person of the Year,” referred to Sen. Elizabeth Warren of Massachusetts as “Senator Karen” after the Democratic lawmaker took aim at him on Twitter.

“Let’s change the rigged tax code so The Person of the Year will actually pay taxes and stop freeloading off everyone else,” Warren tweeted.

“Stop projecting!” Musk fired back. He also included the link to a 2019 opinion piece on Fox News titled, “Elizabeth Warren is a fraud — Her lies about being Native American disqualify her from presidency, Senate.”