A Georgia investigation played a crucial role in helping FBI agents and Israeli authorities home in on the suspect in hundreds of bomb threats against Jewish community centers and other Jewish institutions.

That was one of many details revealed Friday, April 21, when the U.S. Justice Department announced federal charges filed in Georgia and Florida against 18-year-old Michael Kadar, the Israeli-American arrested in Ashkelon in March and accused of a global wave of anonymous threatening phone calls.

“This kind of behavior is not a prank, and it isn’t harmless. It’s a federal crime,” FBI Director James Comey said in the Justice Department press release. “It scares innocent people, disrupts entire communities and expends limited law enforcement resources. The FBI thanks our partners for working with us here at home and around the world.”

The federal announcement did not say whether the United States will seek the extradition of Kadar, who has been in custody since March 23. His attorney and mother have blamed his actions on a brain tumor and have said he has autism.

According to an arrest warrant and criminal complaint issued in Macon, Kadar’s habit of using hacked email addresses, voice-disguising software, Google Voice accounts, spoofing services, stolen Internet access and Bitcoin to anonymously threaten people and places began at least as early as the summer of 2015.

That year, Kadar is believed to have made 11 “swatting” calls — hoaxes intended to provoke SWAT-type police responses — to Athens-Clarke County public schools from Aug. 12 to Dec. 15, sparking the FBI investigation that eventually led to his neighborhood in Ashkelon.

The first of those calls, to Barrow Elementary School in Athens, featured a voice that sounded computer-generated saying, “We are in the school. We see children. We have guns. There will be a blood bath, and something will detonate.”

Each call forced the school to go into lockdown while police searched the building.

Kadar also targeted Gibbs High School and Brickey McCloud Elementary School in Knox County, Tenn., on Aug. 12 and 14, 2015, respectively, according to the Macon complaint. Those were among more than 240 swatting calls, most to schools, placed to the United Stated and Canada through a group of six email addresses linked to Kadar, whose identity has been kept secret under court order in Israel.

But the Macon complaint charges Kadar with making threatening interstate and foreign communications, conveying false information and perpetuating a hoax, and cyberstalking in connection with another recurring target, a private home in Athens. A federal case against Kadar for the 2015 calls would require extra steps under the Juvenile Delinquency Act because he was younger than 18 at the time.

Emergency calls about hostages, threats and a heart attack, all hoaxes, were placed about the same Athens home on three consecutive nights in December 2015. University of Georgia police received a call reporting a home invasion with a man shot and three hostages at the same residence Jan. 3 this year, and Athens police rushed to the scene and found that the call was another hoax. The charges stem from the Jan. 3 incident.

That call came just before the highly publicized series of hoax bomb threats began hitting JCCs, including the Marcus JCC on Jan. 9 and March 15, as well as Jewish schools and offices of the Anti-Defamation League, including the Southeast office in Buckhead.

The Athens investigation — led by the FBI’s Athens Resident Agency, the U.S. Attorney’s Office in Macon, and the Justice Department’s Computer Crime and Intellectual Property Section — uncovered the repeated use of Internet addresses in Israel and reached out to Israeli authorities in October 2015. Israeli police opened a parallel investigation into domestic swatting calls by the summer or fall of 2016, and law enforcement in Australia and New Zealand also shared findings from their swatting investigations.

The Internet addresses used in the Athens calls helped Israeli police identify Kadar’s neighborhood as the source of the threats.

But the Georgia investigation and the FBI-led probe of the JCC bomb threats were separate until the Internet evidence brought them together, leading to FBI agents traveling to Israel and joining in Kadar’s arrest March 23.

“Thanks to the specialized training and expertise of our investigative team, we were successful in identifying, locating and apprehending the person accused of this despicable campaign of threats,” said acting Assistant Attorney General Kenneth E. Blanco of the Justice Department’s Criminal Division.

The investigation of the threats against Jewish organizations was based in Orlando, where two Jewish schools received threats Jan. 4, the day Kadar made at least 31 threatening calls, according to a criminal complaint and arrest warrant filed April 21 in federal court in Orlando.

That complaint charges Kadar with 15 counts of making threatening interstate and foreign communications and 13 counts of willfully making a threat and maliciously conveying false information knowing the same to be false concerning an attempt to kill, injure or intimidate anyone and to damage and destroy any building.

Those charges are limited to Florida threats. But the complaint offers the most detailed picture yet of the wave of bomb threats against Jewish institutions this year. FBI Special Agent Gregory Tarbert said Kadar made at least 245 calls involving bomb or active-shooter threats spread over 15 dates from Jan. 4 to March 7.

The calls included Atlanta’s Intown Jewish Preschool on Feb. 27, a day when Birmingham’s N.E. Miles Jewish Day School and several other schools and Jewish children’s institutions were targeted among 69 phoned threats.

“People, especially children, deserve to feel safe in their communities,” said U.S. Attorney G.F. Peterman III of the Middle District of Georgia. “The violent threats made against schools, families and Jewish community centers sought to rob our citizens of that right. I’m proud that the Department of Justice and the FBI have fought tirelessly to restore that sense of safety.”

The two criminal complaints explain the detailed evidence tying Kadar to the threatening phone calls, such as a USB drive from his bedroom with an “archive of targets” organized by date and location. Folders contain lists of targets in the order in which they were called, recordings of calls, files with the email addresses and other account information used to make the threats, and media reports about the calls.

The details in Kadar’s possession match records subpoenaed from Internet companies, according to the federal complaints. In addition, when recordings of the calls were stripped of the computerized masking, they revealed a speech impediment in the caller that Kadar has.

When Kadar was arrested in Ashkelon, Tarbert wrote, the teenager said he did not do it. Asked what he didn’t do, he said, “The threats.” Pressed on what threats, he specified the “JCC threats,” even though none of the officers had mentioned the JCC threats.

While Kadar previously was linked to threats against Delta Air Lines flights, the Orlando complaint also says he called in a bomb threat against a United Airlines flight Feb. 16.

Doron Krakow, the president and CEO of the JCC Association of North America, thanked federal authorities at the Justice Department and the FBI for their determined investigation and close cooperation with Israeli authorities.

“As the investigation and pursuit of justice, not only in this case but in the cases of all of the perpetrators of these threats continues to unfold,” Krakow said, “we are enormously proud of the extraordinary commitment to safety and security undertaken in JCCs across the United States and Canada each and every day.”