Video of the incident shows the crowd chanting, "No justice, no peace" when, out of nowhere, the pickup truck plows through and slams into one person who was violently thrown back onto the road. Protesters quickly swarmed the truck, banging on it to make the driver stop ... but they fled down Sunset Blvd.
We're told the driver -- who was ID'd and detained by cops but not arrested -- claimed they were trying to escape after being attacked. Police are now investigating to see if the driver was genuinely the victim of an assault or a hit-and-run suspect. As for the protester who was hit ... we're told they were taken to the hospital with non-life-threatening injuries.
A photojournalist told the Los Angeles Times the truck was traveling against the flow of the crowd and definitely instigated the incident.
Police are also investigating a separate incident ... after cops say a white Toyota Prius tried to drive around the same protest.
WATCH: A person driving a white Prius was chased down and by protesters after trying to drive through the crowd in #Hollywood. The group that chased the driver began hitting the car and possibly broke a window. @RoadSageLA was overhead in #Sky9 as it happened. #CBSLApic.twitter.com/OYFMOezUpx