A teenager living in Israel is accused of making scores of hoax bomb threats to Jewish community centres and schools across the US, using an online calling service to disguise his voice as a woman and hide his identity.
Michael Ron David Kadar, 18, who has dual US-Israeli citizenship, has been identified for the first time in criminal complaints filed in Florida and Georgia federal courts.
Kadar, who is Jewish, was arrested in Israel on March 23 and has remained in custody there.
He made at least 245 threatening phone calls between January 4 and March 7, with a significant portion of them targeting Jewish community centres in the US, according to the Florida indictment.
It says Kadar used an online calling service that disguised his voice.
He recorded each of the calls and kept them in files at his home in Ashkelon, along with news articles describing the police responses to the threats, the indictment says.
He paid for the online calls using Bitcoin.
A large antenna at his apartment building allowed him to make long-distance, outdoor wireless connections, the indictment says.
Kadar also is responsible for more than 240 hoax threats called into schools across the US and Canada between August and December 2015, according to the Georgia complaint.
He had not previously been linked to those calls.
US and Israeli authorities have not publicly offered a possible motive.
Kadar's lawyers have said he was home-schooled and suffers from a growth in his head that causes behavioural problems.
The US Justice Department did not say whether it would seek his extradition.