Suddenly, panic broke out in the crowd.
Hundreds of people who gathered for a concert in central Washington on Sunday night ran, some falling and injuring themselves.
The police call for backup.
A little later, helicopters are circling over the otherwise quiet north-west of the city.
The core of a nightlife district in the heart of the American capital is cordoned off.
Sad news at the end of a summer evening when local residents, most of them African Americans, wanted to celebrate Juneteenth Day: a 15-year-old boy died of his injuries;
a policeman and two other passers-by were shot.
What led to the shooting is still unclear.
The perpetrator was still wanted on Monday.
Majid Sattar
Political correspondent for North America based in Washington.
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Police chief Robert Contee said on Sunday evening at the scene of the crime that the concert, which was not approved by the authorities, apparently led to a dispute that triggered the panic.
The shots were fired while the police broke up the event and paramedics treated people who had been injured in the fray.
The police seized several weapons during the evening.
The murder weapon is said not to have been found among them.
Mayor Muriel Bowser said a child was killed at a mass event that was unprofessionally organized and people brought guns to.
Contee announced that legal action against the organizers of the unauthorized concert would be examined.
The Moechella event was intended to celebrate Washington's go-go music, funk music that originated in the capital in the 1960s and 1970s.
In 2019 there was a Moechella concert protesting the gentrification of the district.
On Sunday they gathered to mark Juneteenth Day, which celebrates the end of slavery.
As in many American cities, gun violence has increased again in Washington since the pandemic.