Kurt Eichenwald, senior writer with Newsweek, who had a seizure after being sent a tweet. Credit:Twitter/@kurteichenwald The unusual case has shown how online tools can be deployed as weapons capable of physical harm. The FBI and the Dallas police led the investigation into Rivello, and the police said he sent the strobe light knowing that it was likely to lead Eichenwald, who has publicly discussed his epilepsy, into a seizure. Steven Lieberman, Eichenwald's lawyer, has argued that the use of the strobe light in a GIF, or moving graphic, was akin to sending an explosive or poison in the mail. "This electronic message was no different than a bomb sent in the mail or anthrax sent in an envelope," said Lieberman, who is working on the case as a pro bono service. "It triggers a physical effect." That comparison makes Eichenwald's case different from other claims of harmful attacks using social media. Lawsuits involving stalking and bullying on the internet have focused on how online content, such as disparaging and abusive messages and pictures, can harm victims emotionally and even increase the risk of suicide. But with this case, Rivello is said to have designed the attack specifically around the victim's medical condition.

"This is an interesting and unique case in that there are lots of online attacks that can have physical consequences, such as an attack on an electrical grid or the control of air traffic control," said Vivek Krishnamurthy, an assistant director at the Cyberlaw Clinic at Harvard Law School. "But this is distinguishable because it is a targeted physical attack that was personal, using a plain-Jane tool." Investigators found evidence of the plan to attack Eichenwald from a search of Rivello's Twitter account, the Justice Department said in a statement. After obtaining a search warrant for Rivello's social media account, investigators found direct messages to other Twitter users about Eichenwald, including one that read, "I hope this sends him into a seizure." Other Twitter messages from Rivello included one that read, "I know he has epilepsy." Investigators also searched one of Rivello's digital accounts and found a screenshot of Eichenwald's Wikipedia page that had been altered to show a fake date of death of Dec. 16, 2016, the day after the strobe light attack, the Justice Department said. The digital account also contained screenshots from epilepsy.com with a list of commonly reported epilepsy seizure triggers. The attack drew attention from the news media as thousands of Twitter users witnessed the sequence of events unfold live on the social media site.

Eichenwald, 55, who has about 318,000 followers on Twitter and has written four books, including The Informant, had been critical of Donald Trump throughout his presidential campaign. Eichenwald suspected that the attacker, who operated under the pseudonym "@jew_goldstein" on Twitter, was a supporter of Trump. Twitter has since suspended the account. Late in the evening on December 15, Eichenwald went to his home office in Dallas and saw that @jew_goldstein had replied to a Twitter post with a GIF. When Eichenwald clicked on the file, the strobe light triggered the seizure, his lawyer said. Eichenwald fell to the ground. His wife, Theresa, found him on the floor and saw the Twitter post on his computer screen. She called 911 and then replied on Twitter: "@jew_goldstein This is his wife, you caused a seizure. I have your information and have called the police to report the assault." Eichenwald was incapacitated for several days, lost feeling in his left hand and had trouble speaking for several weeks, according to his lawyer. Soon after, he contacted the Dallas district attorney's office. In state court, Eichenwald's lawyer filed for permission to serve a subpoena of Twitter to gain access to the account for @jew_goldstein. The social media company indicated it would cooperate, which drew protest from an anonymous "John Doe" filing that was intended to quash the subpoena.

Investigators would not say how they tracked down Rivello. Court documents were not immediately available. Rivello will be transferred to Dallas, where Eichenwald lives, to appear before the District Court for the Northern District of Texas. Eichenwald used Twitter on Friday to thank officials for their work on his case. He said that since the December 15 message, 40 more accounts have sent him strobe light images. Loading "Details of their cases are with the FBI. Stop sending them," he wrote on Twitter. The New York Times