The incident occurred during a "No Kings" protest on June 14.
According to the LAPD, the officer fired one round of the less-lethal ammunition after Jack Kearns allegedly broke through a police skirmish line.
Thousands turn out for 'No Kings Day' protest in downtown LA
Footage from multiple officers' body cameras shows that Kearns fell to the ground after being struck by the projectile. He was taken to a hospital for treatment.
Last month, Kearns told ABC7 that he was hospitalized for three days, adding that his injuries included brain bleeding.
Kearns is one of several people who filed lawsuits against law enforcement over their use of force during recent protests.