A man was run over by a police car, as the vehicle was driven into a crowd of people as they tried to block the road at the intersection of South Ninth Street and Pacific Avenue in Washington.
The accident occurred in downtown Tacoma, where about 100 people gathered, according to local police.
Videos on social media showed the police SUV pulling back, then advancing toward the crowd, knocking out several pedestrians to the ground, apparently running over at least one of them.
Then the car drove away, as witnesses started screaming, shocked by the horror of the accident.
The police were called to the scene, after they banned movement there.
A witness said that the police car collided with a crowd of at least 20 people.
Police said that a person was taken to hospital, and it was not clear the nature of his condition.
Investigations are underway into the accident.