Lucy Richards, 57, of Tampa, was indicted on four counts of transmitting threats in interstate commerce.
Richards made a series of death threats to the parent, who now lives in South Florida, the statement said.
Wifredo and George Piro, special agent in charge of the Federal Bureau of Investigation's Miami field office, said Richards is accused of making the threats because she believes the massacre at Sandy Hook was a hoax and never took place.
In recent years, conspiracy theorists have posted videos on the internet claiming to show evidence that the Sandy Hook shootings were a hoax, arguing that the event was staged to erode support for Second Amendment rights to bear arms. Yet to our horror, we have found that there are some in this society who lack empathy for the suffering of others. A teacher in the Newtown School District told a court in September that he had brought a weapon to school because he feared for his safety after receiving what he said were threats from conspiracy theorists. Lanza, who murdered his mother before the massacre, then fatally shot himself.
The Sandy Hook massacre in Newtown, Connecticut, on December 14, 2012, was one of the worst mass shootings in USA history, resulting in the deaths of 20 children and six adults. She is due to appear in court in Fort Lauderdale on December 19. Court records didn't list an attorney for her.