A shopper pepper-sprayed other bargain hunters and robbers shot at customers to steal their Black Friday purchases, marring the start of the U.S. holiday shopping season, according to authorities.

Up to 20 people were injured after a woman used pepper spray at a Walmart in Los Angeles to get an edge on her competitors. In a second incident, off-duty officers in North Carolina used pepper spray to subdue rowdy shoppers waiting for electronics.

A man was in critical but stable condition after being shot by robbers in a parking lot outside a Walmart In San Leandro, California, at 1:50 a.m. (0950 GMT), 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 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.

Black Friday is the busiest day of the year for U.S. stores.

'SENSELESS ACT'

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

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

When customers tried to grab merchandise from the pallets before the sale time, the off-duty officers 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 on Friday demanding her purse as she and companions put their purchases into a car trunk near a Walmart, police said.

The shopper was hospitalized. Her condition was not known.

A Cave Creek, Arizona, Walmart was evacuated and shopping halted temporarily Thursday night after an apparent explosive device was found in an employee break room, Maricopa County Sheriff's Department spokesman Christopher Hegstrom said.

We sent a robot in, Hegstrom said, adding that the device was removed and the store was reopened after bomb squad dogs were sent through the facility.

In Manhattan, a group of shoppers upset that Hollister's flagship store was not opening at midnight like other locations apparently broke into the store and stole a large quantity of clothing, police said. No arrests have been made in the burglary.

(Reporting by Barbara Goldberg in New York, Harriet McLeod in South Carolina, Joe Rauch in North Carolina, Jessica Wohl and Eric Johnson in Chicago, Aman Ali from Ohio, Mary Slosson in Colorado; Editing by David Bailey and Paul Simao)

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