A 15-year-old boy was killed and three citizens injured after a shooter fired at a crowd during an unauthorised music event in Washington DC on Sunday, The New York Times reported.

Metropolitan Police Department Chief Robert J Contee said that a police officer was among those injured. Details about the shooter are not known yet.

“The police officer and two victims are recovering at a hospital,” Contee said during a media briefing. “The shooting is believed to have been a result of a brawl.”

Contee said that the police had shut down the event after violence erupted earlier in the evening, including a fight between those who attended the event. He said that the event was shut down after a “second incident” but did not describe what it was, reported CNN.

After the second incident, as the crowd was dispersing “several individuals were shot”, Contee said.

The police chief said several illegal firearms were discovered earlier in the evening, including one from one of the persons who was shot at, according to CNN.

“Illegal firearms in the hands of people who should not have them make events like this unsafe for people,” he said.

Mayor Muriel Bowser said there was a need to secure permits for events in the city.

“We have a child who was killed today at an event that did not have any proper planning for the number of people who were here and with guns involved,” Bowser told reporters. “The [police] chief and I will continue to make sure we have the resources we need on these corridors and all of our corridors but we need some accountability here.”

The police chief said that someone should be held accountable for holding the event without a permit.

“This is one of the reasons we don’t want unpermitted events taking place in our city,” he added. “Unfortunately, things like this can happen when you have the wrong mix of people, or people who introduce firearms into a situation.”

Sunday’s attack in Washington is an addition to a spate of mass shootings that have taken place in the United States recently.

On June 10, three workers of a manufacturing plant in Maryland were killed after their colleague opened fire.

On June 4, three persons died and 11 were injured after shooting in Philadelphia. On June 1, four persons were killed by a shooter on a hospital campus in Tulsa city of Oklahoma. The shooter, who was carrying a rifle and a handgun, was also killed.

On May 24, a gunman had shot dead 19 children and two adults at the Robb Elementary School in Texas. This was one of the deadliest attacks at an American school since a gunman killed 26 people, including 20 children, in a rampage at Sandy Hook Elementary School in Connecticut in 2012.

The incidents have sparked countrywide debate with the ruling Democrats calling for gun control, and the Republicans demanding better security at schools.

On June 4, United States President Joe Biden urged legislators to ban assault weapons or at least raise the minimum age to buy them.