The holiday shopping season got off to an ugly start as a shopper pepper-sprayed rivals in a battle for bargains and robbers shot shoppers to steal their Black Friday purchases, police said on Friday.

Up to 20 people were injured after a shopper used pepper spray in California to get an edge on rivals and in a second incident, off-duty officers in North Carolina used pepper spray to subdue rowdy shoppers waiting for consumer electronics.

In San Leandro, California, a man was in critical but stable condition after being shot by robbers in a parking lot outside a Walmart at 1:50 a.m. local time, Sergeant Mike Sobek said.

The man was in a group of men headed for their car after shopping when robbers confronted them and a fight ensued, Sobek said. The man's shopping companions held down one of the robbers until police arrived and took him into custody.

It doesn't look like they got away with anything. They weren't expecting these guys to fight back, Sobek said.

In Los Angeles, authorities were reviewing security tapes to track down a Hispanic woman in her 30s who pepper-sprayed a crowd at a Walmart as customers swarmed for Xboxes on sale late Thursday, Los Angeles police Sergeant J. Valle said.

They were opening a package to try to get some Xboxes from a crate and this lady pepper-sprayed a whole bunch of people in order to gain an advantage over the Xboxes, Valle said.

Firefighters treated and released up to 20 people injured in the incident at a Walmart in Northridge, California, authorities said. It was not known whether the woman actually purchased the Xboxes, Valle said.

Off-duty police officers working as security for a Walmart in Kinston, North Carolina, used pepper spray to keep shoppers at bay who were anxious for the midnight Thursday start of an electronics sale, authorities said.

The already rowdy atmosphere intensified when employees began to bring out palettes of electronics merchandise, Kinston director of public safety Bill Johnson said.

When customers tried to grab merchandise from the palettes before the sale time, the off-duty officers, who were hired as store security guards for the event, discharged pepper spray to restore order, Johnson said. One man was arrested for failing to follow officers' orders, he said.

No one was pepper sprayed in the face, Johnson said, adding that he was unaware of any injuries.

Walmart is the U.S. discount store unit of Wal-Mart Stores Inc. A company spokesman, Greg Rossiter, said violence at a handful of stores marred an otherwise safe start to the holiday shopping season at thousands of Walmart stores.

The San Leandro shooting was a senseless act of violence and our thoughts and prayers are with the customer and his family during this difficult time, Rossiter said.

In another incident, a woman was shot in the foot by a robber who accosted her in Myrtle Beach, South Carolina, early Friday demanding her purse as she and companions put their purchases into a car trunk near a Walmart, police said.

When Tonia Robbins, 55, screamed, one of her companions reached into the car, pulled out a revolver stashed in the console and pointed it at the robber, who ran off with Robbins' purse, valued at $40, police said. She then fired two or three warning shots into the air.

Robbins was hospitalized and her condition was not known.

(Reporting by Barbara Goldberg in New York, Harriet McLeod in South Carolina, Joe Rauch in North Carolina and Jessica Wohl in Chicago; Editing by David Bailey)

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