A former journalist has been arrested on suspicion of making bomb threats to Jewish organisations, posing as his ex-girlfriend.
Juan Thompson, 31, was taken into custody on Friday morning and is accused of emailing threats to Jewish centres, including a museum.
One email referred to a "Jewish Newtown" - apparently alluding to a massacre at a Connecticut school in 2012.
The hoax threats stoked fears of a resurgence in anti-Semitism and forced some centres to be evacuated.
Prosecutors said Thompson aimed to frame his ex-girlfriend after she dumped him, portraying her as an anti-Semite.
He initially began emailing the threats using his own name, accusing his ex on Twitter of trying to frame him, it is alleged.
He later sent threats pretending to be her, said prosecutors.
On 24 February, he allegedly posted on Twitter: "Know any good lawyers?
"Need to stop this nasty/racist #whitegirl I dated who sent a bomb threat in my name."
Thompson was a reporter for the Intercept, a news website, until he was fired last year for allegedly inventing sources and quotes.
After his girlfriend broke up with him in July 2016, Thompson began a sustained harassment campaign against her, prosecutors said.
A day after the relationship ended, Thompson sent an email to her boss, purporting to be from a producer at a national news organisation.
The email claimed she had been pulled over for drink driving and sued for spreading a sexually transmitted disease.
Thompson later threatened to publicise nude photos of her, prosecutors said.
He also sent a message to a national children's welfare organisation, claiming she admitted watching child pornography.
Thompson is due to appear in federal court in St Louis on Friday, facing one count of cyberstalking.
The ex-girlfriend could not be reached for comment.