Video posted on YouTube shows two men use a wooden pallet to ram four police officers in riot gear. One officer’s helmet flew off from the force of the attack.

Another attack came from a man carrying what appears to be a snare drum, and using it to hit a 5-foot-1, 115-pound female officer in the back of her head. Despite wearing a helmet, the officer still sustained a concussion.

“This is a serious crime against a Los Angeles police officer who was just doing her job, as thousands of police officers did yesterday,” LAPD Chief Charlie Beck said. “This was a cowardly attack from the rear, entirely unprovoked, that could have seriously, seriously injured this young police officer and ended her career, and even ended her life.”

Those suspects will face felony charges of assault on a police officer when identified.