The Los Angeles Police Department did not immediately respond to CNN's request for comment.

"If LAPD didn't know cameras were on they would've done much WORSE," Sampson wrote on Twitter about the incident.

"They're organized crime, continuing the legacy of slave catching."

Sampson said he went to the emergency room after the incident for his injuries, photos of which he also posted on Instagram.

Sunday marked the sixth day of protests.

Though many of the nationwide protests began peacefully, some turned violent.