Turns out it was fake. Some sort of glitched April Fool's.
No word on the perpetrator, but he attacked with a big knife, so maybe Islamist.
WASHINGTON (AP) — In a story April 2, 2021, about a car ramming into a police barricade at the U.S. Capitol, The Associated Press erroneously referred to Louis Farrakhan as the founder of the Nation of Islam. He is its longtime leader, not its founder.