The suspects' Facebook pages show their support of the Confederate flag and pro-gun militias.
Minneapolis police have said that the suspects are three white males, but have not confirmed whether they are white supremacists.
Investigators have refused protesters' demands to see video of the shooting or to identify the cops who were involved.
Witnesses say police handcuffed Jamar Clark and shot him "execution style."
"To be a person of color in the city is to be over policed, with law enforcement aggressively arresting people for low-level offenses."