Security experts say houses of worship

After a massacre at a Pittsburgh synagogue on Saturday, President Donald Trump suggests armed guards belong to security experts said.

"If they had protection inside, the results would have been better," Trump said after the shooting that left 11 dead and six injured, two critically.

Many security experts consider houses of worship "soft targets" – places that are particularly vulnerable to potential attacks, and Jewish institutions often view security threats.

Deadly shots in denominations in recent years include 26 killed at a church in Sutherland Springs, Texas, in 2017; nine at a church in Charleston, South Carolina, in 2015; six at a Sikh temple in Oak Creek, Wisconsin, in 2012; and three at a Jewish Community Center in Overland Park, Kansas, in 2014.

Last year, a firearms training school in Corona, California, added a "synagogue security" class to its list of courses. Previous private training sessions for synagogues were said to be full-fledged, said William Murphy, co-owner of Firearms Training Associates.

The synagogue security class includes how to use a handgun to stop an attacker, he said.

"We believe in an armed response," Murphy said. "There is no way to stop a gun with a gun if there is not a gun on site."

Chuck Diamond, a rabbi at the synagogue who retired more than a year ago, said off-duty police are hired to work during the fall, but there are no guards, and the entrance is open during sabbath.

"It's a nice community," he said.

Jewish institutions have long been targets for domestic terrorists and often deploy armed security, said Rabbi Abraham Cooper, social action director at the Simon Wiesenthal Center in Los Angeles.

It's a policy that gained momentum after the 1999 North Valley Jewish Community Center in Los Angeles that wounded five, including three young children. Many Jewish institutions moved up to security, and the Los Angeles Police Department increased patrols of houses of worship.

"The wake-up call back then definitely had an impact on Jewish institutions," Cooper said.

But, he added, there probably will always be softer targets.

In 1999, white supremacist Buford O. Furrow Jr. drove from Tacoma, Washington, to Los Angeles in search of victims but bypassed the Simon Wiesenthal Center by the center.

Cooper said high-profile security at two other Jewish institutions in Los Angeles prevented Furrow, now serving life at a federal penitentiary, from attacking them.

That's the point of good security, but it also means that it will eventually become victims, Cooper said.

"You have serious security on your perimeter, chances are, with Buford Furrow, the individual might look somewhere else," he said.

Safdar Khwaja, president of the Pittsburgh chapter of the Council on American Islamic Relations, said that it is one of the largest mosques in the world.

In the past few years, Khwaja said, "a lot" of mosques have reached a point where they are expected to be kept safe.

"It's a very sad state of affairs," Khwaja said. "Some feel that they're secure, but they may not be."

Elizabeth Chuck

Elizabeth Chuck is a reporter for NBC News.

Dennis Romero

Dennis Romero is a freelance reporter based in Los Angeles.