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, 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.

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 on 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 US stores.

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.

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