A concert at London's Brixton Academy was halted after shots were fired as American rapper Nas performed on stage.
Nas was promoting his new single, which was released on Monday
Police said two bullets were fired during a set by the husband of pop star Kelis at the south London venue.
The gig was then stopped and the venue evacuated. A 20-year-old man suffered a gunshot wound to the shoulder.
The academy said an inquiry had been launched and dismissed reports shots were fired from the stage on Monday.
A police spokeswoman said officers were called to the academy at 2156 GMT on Monday following reports of shots being fired inside the venue and people running away.
Det Supt Jon Bishop said: "There is nothing to suggest that this man got up on to the stage.
"We have witnesses who saw a man, wearing a balaclava, move away from the crowds and stand behind a pillar - near to the bar area - before he discharged two bullets."
Officers from Operation Trident, which deals with gun crime within the black community, would be taking over the investigation.
London Ambulance Service was also called to the venue, police said.
Police and ambulance crews outside the Academy
Brixton Academy spokeswoman Louise Kovacs said the venue had been evacuated following consultation with police.
She said there was "a high level of security" at every event.
More than 100 security staff had been working at the show and concert-goers passed through scanning and security checks at the entrance to the venue.
Nas has been touring the UK to promote his double A-side single Just A Moment and No One Else In The Room.