SACRAMENTO (AP) — The only white supremacist charged in a 2016 melee at the California state Capitol that injured at least 14 people was sentenced Wednesday to four years in prison.

William Scott Planer, 36, pleaded no contest in April to assault likely to produce great bodily injury. Sacramento County prosecutors say he knocked a defenseless person unconscious with a pole during a fight between members of the white-nationalist Traditionalist Worker Party and anti-fascist counter-protesters.

READ MORE: Twitter To Pay $809 Million To Settle Class Action Lawsuit Brought By Investors

A social media video shows the counter-protester trying to rise to her feet from the Capitol lawn after losing a fistfight with another member of Traditionalist Worker Party. Planer runs up behind her and hits her in the head with a pole, using a full baseball bat-like swing. She fell unconscious before three other counter-protesters dragged her away.

He was previously convicted of a Placer County robbery in 2001 and was arrested in 2017 on suspicion of pasting stickers reading “Fight Terror, Nuke Israel” on the front door of a Colorado Springs, Colorado, Jewish center.

Three counter-protesters are preparing for trial this fall on charges from the same confrontation.

READ MORE: KPIX Original Report: SF Mission Bay Sidewalks Sinking But City Won't Fix 'Private Property'

At least 14 participants were stabbed or had cuts and bruises, with two surviving critical stabbings. Police also recovered a loaded gun after about 20 white nationalists were confronted by at least 200 counter-protesters.

Independent observers and participants alike criticized police for not moving more quickly to separate the groups.

The Traditionalist Worker Party had a permit to rally at the Capitol, and a California Highway Patrol investigator previously testified that police knew for weeks that a group called By Any Means Necessary and other counter-protesters calling themselves anarchists, anti-fascists, socialists or communists planned to disrupt the gathering, likely using violence.

More than 100 law enforcement officers were caught off guard when the two groups began battling earlier than they had anticipated.

MORE NEWS: Motorcyclist Airlifted To Hospital After Crash Near Bethel Island

Prominent San Francisco Bay Area anti-fascist leader Yvonne Felarca is among the three counter-protesters facing charges including assault and inciting and participating in a riot. She goes by Yvette Felarca while leading and speaking for the group known as BAMN. Her attorney previously said she was among those stabbed during the confrontation.