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By Lucy Bayly

Shares in gun manufacturers rallied Monday after the nation witnessed its deadliest mass shooting in modern history.

Law enforcement officials in Las Vegas said Stephen Craig Paddock, 64, of Mesquite, Nevada, opened fire from his room at the Mandalay Bay hotel on a crowd of about 22,000 concertgoers, killing at least 58 people and wounding over 500.

After the tragedy, shares in American Outdoor Brands (formerly known as Smith & Wesson) went up by 7 percent; Sturm Ruger, known for its semi-automatic and single-shot rifles, topped out at almost 6 percent.

It’s an all-too-familiar pattern after an all-too-familiar situation: Following a mass shooting, traders buy up shares in gun companies in anticipation of fearful citizens stocking up on firearms to defend themselves.

Related: Sen. Murphy Tells Congress to ‘Get Off Its Ass’ on Gun Control

Rommel Dionisio, managing director at Aegis Capital, told CNBC that the gun industry saw a “two- to three-month surge in firearms sales” after last year’s massacre at the Pulse nightclub in Orlando, Florida, and also after the shooting in San Bernadino, California, in 2015.

It’s been a choppy year for gun stocks: Shares soared ahead of the presidential election on fears that a Democratic president would tighten up gun control, only to fall after Donald Trump’s victory, as fears of stricter policies eased.

Following a banner year for the industry — guns brought in an estimated $51 billion in 2016, according to MarketWatch — American Outdoor is at a more-than-two-year low, down 46 percent since the election; Sturm Ruger is down 20 percent in the same period.

Hillary Clinton tweeted Monday morning: “Our grief isn’t enough. We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again.”

She also squarely addressed gun control:

Las Vegas casino operators saw their shares fall Monday, too. MGM Resorts, which owns the Mandalay Bay hotel from which the shooter fired, was down almost 5 percent in pre-market trading. Wynn Resorts also dipped.

“Our thoughts and prayers are with the victims of last night’s tragic events. We’re grateful for the immediate actions of our first responders,” MGM Resorts tweeted after the shooting.