According to police, a shooter opened fire along the route of an Independence Day carnival in the Suburban town of Highland Park, killing at least five people and wounding at least 16.
Hundreds of paradegoers, some visibly bloodied, fled the route, having left behind chairs, baby strollers, and blankets.
The parade was abruptly halted about 10 minutes after it began, trying to send people fleeing for safety, according to the Chicago Sun-Times.
Police officers have secured the area, but the gunman has yet to be apprehended. Highland Park declared that all July 4th celebrations had been canceled as a result.