Police were picking through CCTV footage to identify the gunman who opened fire on revellers at an urban music event.
Three men aged 20, 23, and 25 were recovering in hospital from gunshot wounds after being blasted at the venue in Birmingham.
A fourth victim, a 25-year-old woman, was released from hospital following treatment.
The victims, who are from the Birmingham and Wolverhampton areas, were shot at the Custard Factory arts centre in Gibb Street, West Midlands Police said.
Police, who said the offender was described as a black man, are analysing CCTV footage from the area as part of a "major inquiry" into the shooting.
Detective Inspector Tom Chisholm said: "Police inquiries are ongoing and forensic examinations of the scene are under way.
"We have a number of statements to take but the offender is described as a black male who may have been part of a larger group."
He added: "It's believed there were a large number of people at the venue, which was hosting an urban music event, and we are appealing for them to urgently contact police with any information they may have.
"All gun crime is treated seriously and we want to reassure the local community that we have a team of officers working on this incident and increased patrols in the area."