It is an increasingly common trend: gun sales spike after mass shootings in the U.S. And federal data from November underscores that point, revealing record firearm sales on Black Friday. California also saw the second-highest number of gun purchase applications of any month in the state's history, the Sacramento Bee reports.

RELATED: Why the U.S Has the Worst Mass Shooting Problem in the World

Of course, gun sellers offer bargains on Black Friday, just like any other American retailer, and that serves as one explanation for the spike. But experts say that mass shootings also contribute to increased firearm sales, especially after the Columbine, Aurora, and Newtown massacres.

The Sacramento Bee - sacbee.com

This Black Friday, the FBI processed a record 185,345 background checks for prospective gun purchasers through the National Instant Criminal Background Check System. That's about two background checks per second on the day that a mass shooter opened fire at a Planned Parenthood clinic in Colorado, killing three people.

But while that number itself is remarkable, it does not accurately reflect the total number of gun sales on the unofficial American shopping holiday. The federal system only looks at people who attempt to purchase firearms from federally licensed deals and for permits to carry guns. About 40 percent of guns are sold through unlicensed dealers, making it difficult to determine the actual number of sales in the U.S.

"The previous record for the most background checks in a single day was Dec. 21, 2012, about a week after 20 children and six adults were shot to death in a Connecticut elementary school," the Associated Press reports. "The week following the massacre at Sandy Hook Elementary saw the processing of 953,613 gun background checks."

Wikimedia - wikimedia.org

This year has seen record gun sales on a monthly basis, according to federal data. That might be a response to national debates surrounding gun control — politicians have regularly called for reform in the wake of mass shootings, leading critics of gun regulation to stock up — but it could also be the product of fears over the reality of everyday violence.

RELATED: 13 Heartbreaking Times Pres. Obama Responded to Mass Shootings

"I think so many Americans sometimes feel that there is nothing we can do about it," President Barack Obama said in response to the attack in San Bernardino. "It's going to be important for all of us, including our legislatures, to see what we can do to make sure that when individuals decide that they want to do somebody harm, we make it a little harder for them to do it because right now, it's too easy."