A prominent member of the Department of Government Efficiency was beaten in an attempted carjacking in Washington this week, prompting President Trump to renew his threat of a federal takeover of the city.

The victim was Edward Coristine, a 19-year-old software engineer known by his online sobriquet, Big Balls, according to the police, who said he was surrounded and attacked by 10 young assailants outside his car.

In a social media post on Tuesday afternoon, Mr. Trump shared a photograph that appeared to show Mr. Coristine lying in the street bleeding, battered and shirtless, writing that crime in the nation’s capital was “totally out of control,” though the city’s crime rates have been falling.

“If D.C. doesn’t get its act together, and quickly, we will have no choice but to take Federal control of the City,” he said.

Police officers arrested two 15-year-old suspects, a boy and a girl, both from Maryland, at the scene, according to authorities. Officials said the episode happened in the early morning hours on Sunday in an upscale neighborhood less than two miles from the White House. The two teenagers were charged with unarmed carjacking. The police said they were seeking additional suspects.