A shooting in Washington, D.C., early on Sunday morning left at least one person dead and 20 people wounded, the authorities said.

Christopher Brown, 17, was pronounced dead at a hospital after the shooting, Peter Newsham, chief of the Metropolitan Police Department, said at a news conference on Sunday.

An off-duty police officer was shot and in critical condition, “struggling for her life,” the chief said. She has been an officer with the department for one year, he said.

The other injuries were not life-threatening, he said. One of the injured was a 17-year-old and the rest were adults, he said.

The shooting happened shortly after midnight between the Anacostia River and Fort Circle Park in the city’s southeast quadrant and appeared to have involved at least three people opening fire from separate points at the same time, Chief Newsham said.

He called the shooting an “isolated incident” in a “very safe community.”

The site of the shooting was “some kind of a social gathering” with food being served, music playing and hundreds of people present, he said. The organizers of the event did not have a permit, he said.

A police spokesman earlier on Sunday said the event appeared to be a block party.

A motive for the shooting remained under investigation.

It was not clear why the off-duty officer was at the gathering, the chief said.

Muriel Bowser, mayor of the District of Columbia, said the party was in violation of coronavirus restrictions that prohibit gatherings of more than 50 people.