The usual mantra with stock purchasing is that you buy on the rumor and sell on the news.

News of the latest massacre has upended that as gun manufacturers had a big morning on Wall Street hours after a mass shooting in Las Vegas left dozens dead and hundreds more injured. Gun stocks frequently tick up after major shootings in the belief there will be a run on guns before anticipated tighter controls. Over the years, we've seen the buying sprees continue, but not the tighter controls.

At the market's 4 p.m. close:

Sturm, Ruger (RGR) was up $1.80 (3.48 percent), to $53.50. RGR hit a high of $55.13 Monday morning before profit-taking.

American Outdoors Brands (AOBC) was up $0.49 (3.21 percent), to $15.74. AOBC, which used to be called Smith & Wesson, hit a high of $16.50 Monday morning.

Stock news was not so good, however, for companies that own Las Vegas casinos.

MGM (MGM), which counts the Mandalay Bay — from where the gunman opened fire — among its casino holdings, was down $1.82 (5.58 percent), to $30.77, near its daily low of $30.695.

Wynn Resorts (WYNN) was down $1.85 (1.24 percent), to $147.07. WYNN hit a low Monday of $145.40.

In comparison, the Dow was up 0.68 percent to 22,557.60 and the NASDAQ up 0.32 percent to 6,516.72.