A woman who allegedly fired pepper spray at other customers during a Black Friday sale has surrendered to authorities, Los Angeles police said Saturday.

Police Sgt. Jose Valle said the woman who allegedly caused minor injuries to 20 shoppers at a Los Angeles-area Walmart turned herself in Friday night.

She is currently not in custody but could face battery charges, Valle said. The woman's identity was not released, but police said they plan to release more details Saturday morning.

The attack took place about 10:20 p.m. Thursday shortly after doors opened for the sale. The store had brought out a crate of discounted Xbox video game players, and a crowd had formed to wait for the unwrapping. Valle says the woman began spraying people in order to get an advantage.

The incident was among those nationwide in which violence marred the traditional kickoff to the holiday shopping season.

In the most serious case, a robber shot a shopper who refused to give up his purchases outside a San Leandro, Calif., Walmart store, leaving the victim hospitalized in critical but stable condition.

Police in San Leandro, about 15 miles east of San Francisco, said the victim and his family were walking to their car around 1:45 a.m. Friday when they were confronted by a group of men who demanded their shopping items. When the family refused, a fight broke out, and one of the robbers pulled a gun and shot the man, said Sgt. Mike Sobek.

Meanwhile, police in suburban Phoenix came under fire when a video was posted online showing a 54-year-old grandfather on the floor of a Walmart store with a bloody face, after police said he was subdued Thursday night trying to shoplift during a chaotic rush for discounted video games.

The video, posted on YouTube, shows Jerald Allen Newman unconscious and bloodied as outraged customers yell expletives and say "that's police brutality" and "he wasn't doing anything."

In a police report that redacted the names of officers and witnesses, Newman's wife and other witnesses said he was just trying to help his grandson after the boy was trampled by shoppers, and only put a video game in his waistband to free his hands to help the boy.

Larry Hall, assistant chief of Buckeye police, said Newman was resisting arrest and it appeared the officer acted within reason.

Hall said the officer decided to do a leg sweep and take him to the ground but the man unfortunately hit his head.

"The store was incredibly crowded, and I was concerned about other customers' safety," the officer wrote in his police report.

Hall said Newman, who had a bloody nose and received four stitches on his forehead, was booked on suspicion of shoplifting and resisting arrest.

In Sacramento, Calif., a man was stabbed outside a mall Friday in an apparent gang-related incident as shoppers were hitting the stores.

The victim was taken to a hospital with non-life-threatening injuries, police said.

The stabbing stemmed from a fight between two groups around 3 a.m. in front of a Macy's department store at the Arden Fair Mall.

No arrests have been made. Police were hoping surveillance video will help identify the suspects