Miski Noor, a media contact for Black Lives Matter, said "a group of white supremacists showed up at the protest, as they have done most nights."
One of the three counterdemonstrators wore a mask, said Dana Jaehnert, who had been at the protest site since early evening.
When about a dozen protesters attempted to herd the group away from the area, Noor said, they "opened fire on about six protesters," hitting five of them. Jaehnert said she heard four gunshots.
The attackers fled. No arrests had been made by midnight Monday. Police said via their Twitter feed that they are searching for three white male suspects.