Police officers clash with a protester on the fourth night of demonstrations over recent grand jury decisions in police-involved deaths on December 6, 2014 in Berkeley, California. (Photo by Stephen Lam/Getty Images)

BERKELEY, Calif. — Two officers were injured as a Northern California protest over police killings turned violent, with protesters smashing windows and throwing rocks and bricks at police, who responded by firing tear gas, authorities said.

Several officers were struck, but there were just two reports of injuries, Berkeley police spokeswoman Jenn Coats said. A Berkeley police officer received hospital treatment for a dislocated shoulder after being hit with a sandbag, while another sustained minor injuries.

WMC Action News 5 – Memphis, Tennessee

Updated by theGrio: In the video above, an employee at the Radio Shack describes the violent looters who came into his store as white.

“I don’t know why they have white people coming in and shoving black people, you know what I mean? If you’re protesting white-on-black crime you shouldn’t be in this protest if you have white skin,”  

Saturday night’s demonstration against police killings of unarmed black men in Missouri and New York began peacefully, the latest of several in the Bay Area in recent days. But Coats said some protesters later broke away and began throwing rocks, bottles and pipes at officers.

Scores of law officers from several surrounding agencies joined Berkeley Police Department in trying to quell unrest that went on for hours.

Coats said several businesses on University Avenue were vandalized, including Trader Joe’s, Radio Shack and a Wells Fargo Bank branch. She said demonstrators threw wrenches, smoke grenades and other objects at officers, and some squad cars were damaged.

Coats say officers attempting to get the crowd to depart used tear gas.

“Several dispersal orders have been given, and the crowd has ignored the orders. In response to the violence officers have utilized tear gas and smoke in an effort to disperse the crowd,” she said.

At least six people had been arrested by the time the unrest ended early Sunday morning, Coats said.

Local media reports said about 300 to 400 people participated in the relatively peaceful demonstration before splinter groups broke off.

The San Francisco Chronicle reported that at one point, the marchers were face-to-face with a line of about 100 police in riot gear who turned the crowd back.

The newspaper said that it wasn’t just protesters who were hit by tear gas.

Several concerts had let out from downtown sites and concertgoers waiting to pay in a nearby garage were enveloped in a cloud of stinging gas, sending them running into elevators.

KCBS reported that police closed two Bay Area Rapid Transit commuter train stations along the protest route.

Protesters had planned to march from the University of California, Berkeley campus to Oakland’s Civic Center.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.