Israel and Gun Violence; why gun violence is less common in Israel–where many carry guns openly–than in the U.S.:

By Alana Goodman at Commentary Magazine; "Most of the mass shootings that have taken place in Israel were related to the conflict in the region... at least two of these firearm terrorist attacks occurred at schools (both yeshivas). In both cases, the gunmen were not given the chance to end their own lives. They were killed by people at the schools who had guns."....

Goodman links to this article from Tablet Magazine, saying the author, Liel Leibovitz takes a look at why gun violence is less common in Israel–where many carry guns openly–than in the U.S.:
It’s the Jewish state’s gun culture, not its laws, that prevents mass shootings like the one in Connecticut

Israeli girls wear automatic rifles as they dance together during the celebrations for Independence Day in Jerusalem on April 19, 2010.

"The first and most universal one is that ever more stringent gun control is bad policy: As is the case with drugs, as was the case with liquor during Prohibition, the strict banning of anything does little but push the market underground into the hands of criminals and thugs. Rather than spend fortunes and ruin lives in a futile attempt to eradicate every last trigger in America, we would do well to follow Israel’s example and educate gun owners about their rights and responsibilities, so as to foster a culture of sensible and mindful gun ownership."

...." “An armed society,” Nedivi wrote, quoting the science fiction writer Robert A. Heinlein, “is a polite society. Manners are good when one may have to back up his acts with his life.” It may be a bit odd to think of Israeli society as polite, but when it comes to guns it is, and for just the reason articulated by Heinlein: When everyone has a gun, guns are no longer seen as talismans by weak, frightened, and unstable men seeking a sense of self-validation, but as killing machines that are to be handled with the utmost caution and care." 

Can't argue with that. Goodman concludes with this:

I'm sorry that many will find this poster offensive. I just ask
 that you give me an argument against it if you can. I only
wish one of the adults killed at the school had been armed.

"That’s definitely not to argue that arming more people is a solution to mass shootings in America. Israel is different because many of the people who carry guns in public are trained soldiers, and military service is mandatory for almost everyone. The heroes who stopped the gunmen at the yeshivas were reportedly all either soldiers or enrolled in pre-military preparatory programs. But it also contradicts the notion that fewer guns equals more safety. There may be policy responses to the Sandy Hook Elementary shooting that could be helpful in small ways–a review of mental health treatment in this country is warranted, and even a debate about gun laws isn’t a bad idea. But there are no obvious, all-encompassing solutions and anyone who argues otherwise is selling something."