Elon Musk, speaking at a post-inauguration rally, twice extended his arm out above his head with his palm facing down, drawing comparisons to a Nazi salute.

Elon Musk’s controversial gesture, which some interpreted as a Nazi-style salute, drew criticism from Trump’s political opponents and energized fans on the far right.

Elon Musk gave what appeared to be Nazi salutes at a rally held at Capitol One Arena on Monday after the inauguration of Donald Trump in Washington, D.C. And whatever Musk’s intention with the salutes, Americans on social media are extremely uncomfortable as they debate what it could mean for the future of the country.