The flashing image sent to Kurt Eichenwald, a Newsweek senior writer and Vanity Fair contributing editor, on December 15 came with the message: "You deserve a seizure for your post", according to the criminal complaint.
The justice department did not say what motivated the attack, though reports have speculated that it may have been related to Mr Eichenwald's frequent criticism of US President Donald Trump on Twitter.
Eichenwald has written openly about his epilepsy in years past. According to Lieberman, the.gif caused Eichenwald to suffer a seizure that caused a "very, very severe reaction" and that his client was disabled for several days.
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The Justice Department said in a news release that investigators obtained a search warrant and found Rivello's Twitter account "contained direct messages from Rivello's account to other Twitter users concerning the victim".
He told "GMA" that his wife captured a still image from the seizure-triggering animation.
Rivello's iCloud account also contained screen shots from epilepsy.com with a list of commonly reported epilepsy seizure triggers and from dallasobserver.com discussing the victim's report to the Dallas Police Department and his attempt to identify the Twitter user. "Stop sending them", he wrote.
Lieberman said that this tweet wasn't an effort to curb free speech, equating it to sending an envelope of Anthrax spores or a bomb to someone. 'It triggers a physical effect'. The Epilepsy Foundation estimates that certain visual patterns and flashing lights can trigger seizures in about 3% of people with epilepsy. Some even sent more flashing light GIFs at Eichenwald even as he pressed charges and prepared a civil lawsuit against the unknown Twitter account.
Eichenwald later tweeted that he would be taking a short break from Twitter for self-protection and would be speaking with lawyers and law enforcement regarding the attack.