Another American mass shooting. Another rush to buy more guns.

On the Monday after the latest of the bloody rampages that are part of American life, gun sales in Arizona shot up by more than 60 percent and rose by an average of five percent across the entire country. The figures come from the FBI and speak volumes about a gun culture that has long baffled much of the world.

The Federal Bureau of Investigation compared January 10, 2011, with the corresponding Monday a year ago.

So what would prompt Americans to stock up their arsenals in the wake of the shooting in Tucson that killed six people and wounded 14, including Gabrielle Giffords, the congresswoman who was the target of an unhinged 22-year-old who has since been charged with attempted assassination?

To hear gun dealers tell it, demand went up because of fears that the Tucson shooting might lead to tighter gun laws. There was a similar spike in sales after the 2007 mass shooting at Virginia Tech, where a deranged student killed 32 people and himself in the worst such massacre in American history.

Fear of regulation also drove up gun sales after President Barack Obama won the presidency in November 2008. In the first two months of 2009, about 2.5 million Americans bought guns, a 26 percent increase over the same period in 2008.