A 17-year-old boy died and 20 other people were injured — including an off-duty cop left struggling for her life — when gunfire broke out at a block party early Sunday in Washington, DC, police said.

Teen Christopher Brown, who has a 1-year-old son, was killed when multiple shooters opened fire around 12:20 a.m. on Dubois Place in the Greenway neighborhood of Southeast Washington, news station WJLA reported. 

“You had DJs, everybody was down there. It was more women than men,” resident Nelson Bostic — who said the gathering had been a birthday celebration — told news station WTOP.

“Next thing you know, it was like Beirut out here. It sounded like machine guns and everything else that was going on out here.”

Footage posted to social media from the moment shots rang out showed hundreds of partygoers screaming and running from the scene, the Daily Mail reported. 

DC Police Chief Peter Newsham said the victims included an off-duty cop who is now in the hospital “struggling for her life.”

The other victims were brought to various hospitals for non-life-threatening gun wounds, news station WUSA reported.

Newsham said police believe the shooting was an isolated incident.

“There was some kind of dispute, and multiple weapons were produced, and multiple shots were fired,” Newsham told reporters Sunday.

Brown’s mom, Artecka Brown, said her son was an innocent victim and “just wanted to attend a neighborhood party.

“A lot of people know him as just a good person. … He was a king,” she told WUSA. “And that was an innocent life taken for no reason.”

No arrests have been announced in connection to the shooting.