Gun stocks saw gains Monday following the deadliest mass shooting in modern U.S. history. The shares of America's largest gun manufacturers each rose in trading.

Smith & Wesson parent company American Outdoor Brands Corp.'s stock went up 3.8 percent in midday trade, while Sturm, Ruger & Co., Inc. shares jumped 3.9 percent. Vista Outdoor Inc. shares reached a six-week high by climbing 3.0 percent

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Gun stocks tend to rally after mass shootings, according to Business Insider, because conversations about potential gun-control legislation raises speculation that firearms will no longer be readily available. Americans seek to buy guns before any regulations could take effect.

"The market always has an instinctive reaction to events and more and more it's algorithmically induced," Quincy Krosby, chief market strategist at Prudential Financial, told USA Today.

"Traders believe that people will go out to buy guns for self protection; perhaps those who have been thinking about it but who have been debating the merits of the purchase," she added.

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Trump's win removed any fears of regulation, resulting in downward profits for gun companies. Sturm Ruger said in August that its quarterly revenues were down 22 percent from year to date and that earnings decreased by about 50 percent, according to CNN Money. American Outdoor Brands reported a nearly 40 percent drop in sales during its latest quarter.

Shares of MGM Resorts International (MGM), which owns the Mandalay Bay Resort and Casino, dropped 4.6 percent Monday, according to USA Today. Investors sold the stock amid fears that the shooting could affect future bookings.