The footage, released by the LAPD on Friday, shows cops in riot gear moving in to take control of a Hollywood intersection amid an anti police-brutality demonstration on June 2.
One officer yanks a sign out of the hands of a protester, who puts his hands up as another cop pushes him backwards, the video shows.
A third cop then shoots a 40-millimeter projectile at the protester’s crotch at close range.
The department said it launched an investigation into the use-of-force incident on Aug. 19, in response to a Los Angeles Times story and an Instagram post from the protester.
Ben Montemayor, a 28-year-old filmmaker, told the Times he suffered serious injuries to his testicles, with one swelling to twice its usual size, as a result of being shot. He said he was rushed into emergency surgery to preserve his ability to have children.
Montemayor has said he intends to file a lawsuit against the LAPD.
A police spokesman told the Times that Montemayor left the scene and has declined to answer questions from cops since, referring them to his attorneys.
His attorney, Dan Stormer, bashed the police probe, calling the department’s investigations of its own officers “a complete farce.”
“They’re taking evidence and conducting an investigation to protect themselves from the lawsuit that is coming,” Stormer told the Times.
The video shows “a brutal assault” on Montemayor, which is “in some ways, it’s even worse than we thought,” the attorney said.
“It’s not often you see something like this that is so cut and dried, but it’s pretty brutal.”
Department policy requires such projectiles be used only on individuals who present a clear and immediate threat, and who are at least five feet away. Officers are not to use the weapons in response to verbal threats or “mere noncompliance,” according to the Times.
The LAPD’s investigation into the incident is still in its early stages, and no determinations have yet been made as to whether the cops’ actions were appropriate, a spokesman said.