Gun sales slumped after Donald Trump was elected president, but that could change after Sunday's massacre in Las Vegas, the deadliest in modern U.S. history.

It wouldn't be the first time that gun sales have jumped in the wake of a mass shooting.

Handgun sales spiked by 62% in December 2015, following the San Bernardino shootings that killed 14 and the November 2015 terror attacks in Paris, according to Rommel Dionisio, managing director at Aegis Capital and an expert on the gun industry.

And sales were up for several months after the June 2016 attack on the Pulse nightclub in Orlando that claimed 49 lives, climbing about 20% in June, July and August 2016.

The killing spree in Las Vegas left 59 dead and more than 500 injured, and it could prompt Americans to start buying more guns.

"This event in Las Vegas could result in increased demand near-term for firearms as people are concerned about personal safety," Dionisio said.

Related: Gun stocks up after Las Vegas shooting

Guns are already big business. Americans buy 15 million to 16 million firearms per year, Dionisio estimates. According to research from IBISWorld, gun and ammunition stores brought in $8.6 billion in revenue in 2016.

A sales bump is by no means guaranteed. But investors appeared to be betting on one Monday, sending shares of gun maker Sturm Ruger (RGR) up 6%. American Outdoor Brands (AOBC), the company formerly known as Smith & Wesson, gained nearly 7%.

Gun stocks also spiked after both the Pulse and San Bernardino shootings, due in part to President Obama's promises to tighten gun laws. Fears of more strict regulations tend to drive shoppers to buy more guns while they still can, but those stricter law never materialized.

Retailers stocked up on firearms during the 2016 presidential campaign, anticipating a stampede of gun buyers after Hillary Clinton won the race and moved to restrict gun sales.

Instead, Trump won, and gun sales slumped, since it seems unlikely that his administration will strengthen gun control laws. As a result, gun stocks have mostly been lower since the election.

Shares did spike, however, when news broke that the president is considering easing export laws -- a move that would make it easier to sell American guns abroad.

-- CNNMoney's Paul La Monica and Aaron Smith contributed to this story.