It was an act of "competitive shopping"....

Black Friday got off to a dark start in the U.S. as several shootings, a bomb scare and a pepper-spraying shopper marred the annual post-Thanksgiving buying blitz.

The mayhem began late Thursday, as 15 people, including children, were injured after a woman reportedly pepper-sprayed other shoppers at a Los Angeles-area Walmart store.

A fire captain described Thursday night's incident as an act of "competitive shopping," according to the Los Angeles Times.

L.A. Fire Capt. James Carson told the newspaper the woman had armed herself with pepper spray to get the edge on her fellow shoppers at the store in the Porter Ranch neighbourhood.

People pepper-spray people.