Around 20 customers were reported hurt, including children, in what authorities described as an extreme instance of "competitive shopping."
"This was customer-versus-customer 'shopping rage,'" Los Angeles Police Lt. Abel Parga told the Associated Press. "Somehow she was trying to use [pepper spray] to gain an upper hand."
The incident occured as the Porter Ranch branch of Walmart began its sale 10 p.m. Thursday night.
The store was packed with shoppers waiting for the whistle that would signal the start of the sale, witnesses told the Times' L.A. Now blog.
Approximately 100 people were thronging around the video game aisle when over-excited shoppers began ripping the covers off consoles, shopper Alejandra Seminario said:
"People started screaming, pulling and pushing each other, and then the whole area filled up with pepper spray. I guess what triggered it was people started pulling the plastic off the pallets and then shoving and bombarding the display of games. It started with people pushing and screaming because they were getting shoved onto the boxes."
Fire officials were called and the store temporarily evacuated. Several customers were treated for minor injuries including skin and eye irritation and sore throats, the Times said, though firefighters told local television that some of the injuries were caused by shoppers pushing and shoving as they attempted to flee.
Some shoppers said the store had been overcrowded to begin with, describing bargain-hunters tearing down display signs and trampling on fallen merchandise.
The Walmart remained open for the rest of the night.
The National Retail Federation expects 152 million people to hit the shops this weekend, the Guardian said, an increase of 10.1 percent from 2010.