At least one person was killed and over 20 others were shot when a group of people gathered to celebrate Juneteenth at a parking lot in Chicago, police said.
The shooting occurred shortly before 12.30 a.m. on Sunday, local media quoted DuPage County Deputy Sheriff Eric Swanson as saying.
Some victims were hospitalised in DuPage while several got to hospitals on their own, reports Xinhua news agency.
The ages and names of the victims have not yet been released.
No suspect information has been released either.
It was unclear what prompted the shooting, Swanson said.
A witness said people were gathered for a Juneteenth celebration when the gunfire started.
Juneteenth is a federal holiday in the US marked annually on June 19 to commemorated the emancipation of enslaved African Americans.