A shopper in Los Angeles pepper-sprayed her competition for an Xbox and scuffles broke out elsewhere around the U.S. as bargain-hunters crowded stores in an earlier-than-usual start to the madness known as Black Friday.

For the first time, chains such as Target, Best Buy and Kohl's opened their doors at midnight on the most anticipated shopping day of the year. Toys R Us opened for the second straight year on Thanksgiving itself. And some shoppers arrived with sharp elbows.

Near Muskegon, Mich., a teenage girl was knocked down and stepped on several times after getting caught in the rush to a sale in the electronics department at a Walmart. She suffered minor injuries.

On Thanksgiving night, a Walmart in Los Angeles brought out a crate of discounted Xboxes, and as a crowd waited for the video game players to be unwrapped, a woman fired pepper spray at the other shoppers "in order to get an advantage," police said.

Ten people suffered cuts and bruises in the chaos, and 10 others had minor injuries from the spray, authorities said. The woman got away in the confusion, and it was not immediately clear whether she got an Xbox.

On Friday morning, police said, two women were injured and a man was charged after a fight broke out at an upstate New York Walmart. A man was arrested in a scuffle at a jewelry counter at a Walmart in Kissimmee, Fla.

Wal-Mart Stores, the nation's biggest retailer, has taken steps in recent years to control its Black Friday crowds following the 2008 death of one of its workers in a stampede of shoppers. This year, it staggered its door-buster deals instead of offering them all at once.

Wal-Mart spokesman Greg Rossiter said Black Friday was safe at most of its nearly 4,000 U.S., but there were "a few unfortunate incidents."

The incidents were attributed to two converging Black Friday trends: Crowds are getting bigger as stores open earlier and stay open later. At the same time, cash-strapped shoppers are competing for deals on a small number of gifts that everybody wants - tablet computers, TVs and game consoles like Xbox, Nintendo 3S and Wii.

That's a shift from years past, when there was a wider range of must-have items.

"The more the people, the more the occurrences," said Marshal Cohen, chief industry analyst with market research firm The NPD Group.

A record number of shoppers are expected this weekend to take advantage of discounts of up to 70 percent. For three days starting on Black Friday, 152 million people are expected to shop, either online or in stores, an increase of about 10 percent from last year, according to the National Retail Federation.

Thanksgiving weekend, particularly Black Friday, is huge for retailers. Over the past six years, Black Friday was the biggest sales day of the year, and it is expected to keep that crown this year, though shoppers seem to be procrastinating more every year, and the fate of the holiday season is increasingly coming down to the last few days before Christmas.

Last year, the Thanksgiving shopping weekend accounted for 12.1 percent of overall holiday sales, according to ShopperTrak, a research firm. Black Friday made up about half of that.

ShopperTrak is expected to release sales data on Saturday on how Black Friday fared, but a better picture will emerge when major retailers report their November sales figures next Thursday.

In addition to opening earlier than usual this year, some stores offered to match their competitors' prices, rolled out layaway programs or offered more door-buster deals than last year.

Emmanuel Merced and his brother showed up at a Best Buy in New York at 3 p.m. on Wednesday so they could be the first in line when it opened at midnight Thursday to grab a Sharp 42-inch TV for $199.99, a PlayStation 3 with games for $199.99 and wireless headphones for $30.

Merced said he likes camping out for Black Friday and figured he saved 50 percent.

"I like the experience of it," said Merced, who plans to spend $3,000 to $4,000 on gifts this season.

To be sure, not every place was full on Black Friday. With so many major stores opening at midnight, many people stayed up late and shopped early. Then there were those who stuck to their normal routine of going to stores that opened later Friday morning. That left a lull in the hours just before and after daybreak.

At a Target on Chicago's North Side, crowds were light four hours after the store opened at midnight. And door-buster deals, including the typically quick-to-sell-out TVs and game systems, remained piled up in their boxes. Shoppers pushed carts through mostly empty aisles while thumbing through circulars, and employees in Santa hats roamed the store. There was no Christmas music - or any music - playing.

Rebecca Carter, a graduate assistant, began Black Friday shopping at 11 p.m. on Thursday and left Target around 4 a.m. carrying a bag full of pillows. Carter said the crowds were noticeably lighter this year as she and a friend picked up a 32-inch TV for $180 and a laptop for $198, along with toys and pajamas.

"It's quiet," she said. "It was shocking."

Melody Snyder of Vancouver, Wash., had braced herself for anarchy when she got to Walmart at 6 a.m. but was pleasantly surprised when she pulled into the parking lot.

"I got here and thought, 'Where is everyone?'" said Snyder, who found some Barbies and other toys sold out but was still able to find gifts for her three kids.

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Retail writers Mae Anderson and Anne D'Innocenzio are in New York. Sarah Skidmore in Vancouver, Wash., Christina Rexrode in Cary, N.C., Ashley Heher in Chicago and Tamara Lush in St. Petersburg, Fla., contributed to this report.