Shares of some gun makers appear to have spiked shortly after news of a mass shooting in  San Bernardino, Calif.

CNBC's Carl Quintanilla points out that Smith & Wesson's stock jumped roughly 1 percent in the minutes after word of the shooting got out, at around 2 p.m. Eastern. (It's now trading at half a percent below its opening price.)

Meanwhile, shares of Ruger also jumped 1 percent and continued rising through the end of the day.

It's hard to say anything definitive about why the stock prices went up or down. There are only a handful of publicly traded gun companies — one of the few others, Olin Corporation, ended the day down 1.4 percent. Regardless, my colleague Jim Tankersley has noted previously that the past few years have been good for gun investors.

Mass shootings have  had a predictable effect on gun sales. They almost always go up, whether you're talking about Aurora, Columbine, or Virginia Tech. And some may attempt to argue that the recent shootings in Colorado near a Planned Parenthood may lead to similar results — though it's clear that Black Friday is correlated with higher gun sales relative to the rest of the year, anyway.