The suspect stabbed the victim in the upper chest around 2 p.m. Saturday, according to the Los Angeles Police Department. The suspect, seen in photos wearing all black clothing and a dark mask, is now wanted for assault with a deadly weapon.
The suspect was described as possibly white or Hispanic, between the ages of 20 and 30 with long blonde hair. He was last seen wearing a black bandanna, black hoodie, black skinny jeans with holes in the knees and white tennis shoes.
An anti-vaccine protest as well as a counter-demonstration were scheduled for Saturday afternoon on the south lawn of City Hall.
One was a "Choose Freedom March" to protest the "medical tyranny" of mandatory vaccinations and vaccine passports. The counter-protest called itself "No Safe Space for Fascists" to demonstrate against what organizers called "violent anti-vaxxers."
It's not clear exactly how the fight broke out, but video shows groups of people brawling at the scene.
The stabbing victim is expected to be OK.
Anyone with information on the stabbing was asked to call LAPD Central Area Detective Cheng at 213-996-1248. Calls made during non-business hours or on weekends should be made to 877-527-3247.
Anonymous tips can be called in to Crime Stoppers at 800-222-8477 or submitted online at lacrimestoppers.org.
City News Service contributed to this report.