A shooting outside a Missouri mall just before Black Friday has left one teenager with life-threatening injuries, police said.

A 19-year-old person was reported injured at 11:30 pm the night before the infamous shopping holiday, according to a police report. The mall was open until midnight in anticipation of Black Friday shopping, according to its website.

Police said the shot was fired by a man sitting in his car outside the mall, who accidentally discharged his weapon while trying to re-holster it. Authorities have not determined whether the shooting was accidental or deliberate.

Another man was also in the car, police said. The investigation is ongoing, and no arrests have been made. The mall opened on schedule for Black Friday, at 6 am, according to local reporters.

Violence broke out in other areas of the country as well, as shoppers lined up to score their post-Thanksgiving deals. In Alabama, police shut down a mall on Thursday night after several fights were reported.

Black Friday 2017 – in pictures Show all 8 1 /8 Black Friday 2017 – in pictures Black Friday 2017 – in pictures Shoppers reach out for television sets as they compete to purchase retail items on Black Friday at a store in Sao Paulo, Brazil Reuters Black Friday 2017 – in pictures Dozens of Brazilians reach for television sets in a store in Sao Paulo, Brazil EPA Black Friday 2017 – in pictures Dozens of Brazilians reach for television sets in a store in Sao Paulo EPA Black Friday 2017 – in pictures Brazilians reach for television sets in a store in Sao Paulo EPA Black Friday 2017 – in pictures People wait outside a department store in Thessaloniki, Greece AFP/Getty Black Friday 2017 – in pictures People wait in line outside of Best Buy in Norwalk, Connecticut November 23, 2017 for the store to open at 5PM on Thanksgiving Day to take advantage of the Black Friday sales AFP/Getty Black Friday 2017 – in pictures People shop at Macy's department store on Thanksgiving Day. Some stores began their 'Black Friday' sales earlier than the usual date Getty Black Friday 2017 – in pictures Shoppers are seen queuing for the opening of a Game discount store on 'Black Friday' at a shopping mall in Umhlanga, KwaZulu-Natal, Durban, South Africa Reuters

Officers responded to a mall in Birmingham, Alabama shortly after 11 pm, and found two girls fighting while other shoppers looked on. Both were treated by paramedics for minor injuries. The fight was not related to Black Friday sales, police said.

"Hoover Police will have extra officers on site at our retail areas throughout the holiday season to ensure the safety and security of the patrons and stores in our city," the department said in a statement.

What is Black Friday?

Black Friday, once known exclusively for the tide of sales it brings, has in recent years become synonymous with consumer aggression –and occasionally, violence.

In 2013, two men were arrested in Virginia after allegedly engaging in a knife fight over a Walmart parking space. The next year, police in California responded to reports of two women who started a "pushing and shoving match" over a Barbie doll on Thanksgiving night.

Deploying additional security officers on Black Friday has since become common practice at malls across the country. This year, however, some stores are stepping up their security to protect not from shoppers, but from possible shooters or terrorists. In Wrentham, Massachusetts, one outlet mall has installed large plastic barriers to prevent truck attacks like those recently seen in New York and Paris.