A video has surfaced on Facebook that appears to show a Charleston police officer repeatedly punching a woman who was already lying on the ground and restrained by a second officer.

Police officers have a constitutional duty to avoid excessive force when dealing with the public. If we’ve learned anything from the epidemic of police violence aimed at communities of color it’s that justice can only be served when there is a swift, open, and transparent investigation.

While there is much we don’t know about this particular incident, we do know this: the city of Charleston must conduct a thorough investigation that citizens can trust.