This story was originally published Friday and has been updated after additional Jewish community centers and schools were threatened on Monday.

A young Israeli man who also holds U.S. citizenship was arrested in Israel on March 23, in connection with a wave of threats made to Jewish community centers in the U.S. and several other countries in past months, according to the FBI and local authorities. (Jenny Starrs/The Washington Post)

Again and again, the calls have come in.

In Miami, hundreds of young students fled their school building. In Foster City, Calif., parents scrambled to pick up preschoolers whose school suddenly closed for the day. In West Hartford, Conn., elderly women climbed out of the pool mid-swim to evacuate.

And so it went in Albuquerque, in Birmingham, Ala., in Chicago and about 50 other cities — a rash of ominous phone calls, threatening that a bomb had been placed at a Jewish community centers, in more than half the states in the country and one Canadian province since the start of January.

On Monday, the latest wave of calls targeted JCCs as well as Jewish schools in 11 states, according to JCC Association of North America. Two Jewish schools in the D.C. area were among the targets.

No bomb was found after any of the calls, but the threats prompted clamor for President Trump to condemn the anti-Semitism behind the targeting of these Jewish institutions. After initially responding to questions about anti-Semitism with boasts about his electoral-college victory, Trump eventually called the threats to the community centers “horrible” and “painful,” and Vice President Pence paid a visit to a Jewish cemetery vandalized near St. Louis. Another Jewish cemetery, in Philadelphia, was then vandalized.

Now, many Jews are looking to law enforcement, hoping the FBI will find the perpetrator so that the disruptive phone calls will end.

“While we are relieved that all such threats have proven to be hoaxes and that not a single person was harmed,” JCC Association said in a statement following the fourth wave of bomb threats, “we are concerned about the anti-Semitism behind these threats, and the repetition of threats intended to interfere with day-to-day life.”

Each of the calls has come from someone using robo-call technology to mask his or her voice and phone number, said David Posner, JCC Association’s director of strategic performance.

Security experts said that the Internet has made it relatively simple for anyone to obtain this technology, making the task of catching the culprit behind the JCC threats a difficult job.

FBI and Justice Department officials declined to discuss the ongoing investigation into the calls, which began Jan. 9. The FBI’s statement on the investigation said: “The FBI and the Justice Department’s Civil Rights Division are investigating possible civil rights violations in connection with threats to Jewish Community Centers across the country. The FBI will collect all available facts and evidence, and will ensure this matter is investigated in a fair, thorough, and impartial manner.”

Posner said that he has faith that the federal government is taking the investigation very seriously.

“The FBI is making it priority one. I had a briefing to that effect. They’re making it the top priority. When you have four waves of these, affecting 53 different JCCs and 68 separate events, that it not a small number,” Posner said. “This is really an FBI issue. State and local law enforcement can’t solve this. The commonalities of the calls have to be handled at the highest level.”

The nationwide nature of the threats might make the field of possible suspects seem dauntingly large. But threat-assessment consultant Steve Albrecht, a retired San Diego police officer who specializes in studying workplace threats, said a culprit making calls nationwide is often easier to catch than a localized threat.

The FBI has a massive database and can compare a caller’s behavior to that of suspects across the country. “They develop a perpetrator profile,” Albrecht said. “The calls come in at this time of day, say these types of things. They’re this length. People have patterns.”

Albrecht said that he would not recommend evacuating a JCC each time a threat does come in. For decades, bomb threats have nearly never indicated that an actual bomb was present in a building.

“If we evacuate the facility every time somebody makes a bomb threat, that just encourages them to do more,” Albrecht said. “It’s a tremendous waste of time and energy, and it frightens people.”

Instead, he recommends sending bomb-sniffing dogs to check the building without evacuating and interviewing employees about whether they have noticed any suspicious packages or anything else amiss.

Posner said each JCC has its own protocols for responding to risky situations, and in many cases that does mean evacuating.

JCC staffers also follow recommendations from the Department of Homeland Security about what to do when a threatening caller is on the phone. The recommendations include keeping the caller on the line for as long as possible, asking questions about where the bomb is located and what it looks like, and noting details such as the exact wording of the threat and any potentially revealing background noises.

Posner said JCC staffers have long been trained to use these federal checklists. After putting them in practice so many times in recent weeks, staffers are now “terribly proficient,” he said.

The 100-year-old JCC Association has preschools, camps, gyms and other programs across North America. In many communities, Jews and non-Jews attend the schools and recreational programs. Posner said the waves of threats have not decreased attendance lately.

“We have been very gratified by the response, that people are not withdrawing their kids, not suspending their memberships. They are staying with the JCCs,” Posner said. “A situation like this really demonstrates how people feel about their JCCs. I think they’ve really come to feel the support, the caring, I dare say the love of their communities for them.”

This is not the first time JCCs have been threatened, and in the worst cases they have experienced deadly violence. In 2014, an avowed white supremacist fatally shot two people outside a Kansas JCC and a third person at a nearby Jewish retirement home. Another self-proclaimed white supremacist opened fire on a JCC in Los Angeles in 1999, shooting at the building 70 times and wounding five people inside, including three children.

This history of being targeted means JCCs are adept at security and may be able to share information with the FBI more ably than other organizations, Albrecht said. But Posner reminded that this is a matter for federal investigators.

“It’s not on us to solve the case. It’s the responsibility of law enforcement, especially the FBI,” Posner said. “And they’re working on it. We have been given assurances, and we believe those assurances, that this is a difficult case.”

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