After the initial incident, "More than 40 ppl sent strobes once they found out they could trigger seizures", tweeted Eichenwald.
John Rayne Rivello, 29, of Maryland, sent Kurt Eichenwald an animated image with a flashing light on Twitter in December, causing the seizure. The FBI confirms to Heat Street that an arrest has been made.
Eichenwald has been public about having epilepsy.
It was sent after an interview on Fox News when Eichenwald was grilled over a tweet he posted last September claiming Donald Trump suffered a nervous breakdown in 1990 and was institutionalized.
Meanwhile, Newsweek identified the suspect as John Rivello, who was arrested early Friday at his residence in Salsbury, Maryland.
The Twitter message told the recipient "you deserve a seizure for your post", according to a statement from the Justice Department.
It immediately triggered a seizure in Eichenwald, leaving him incapacitated for several days.
The search warrant also found screenshots on Rivello's iCloud account "from epilepsy.com with a list of commonly reported epilepsy seizure triggers", the Justice Department said, and other screenshots related to Eichenwald.
Only around three in every hundred people with epilepsy suffers from the photosensitive kind, according to the charity Epilepsy Action.
Called photic or pattern-sensitive seizures, these occur when people with epilepsy see a series of images or video that fall into a certain range of color, pattern and frequency. The FBI hasn't issued a press release regarding the arrest as of publication time, and a spokesperson hasn't responded with additional information yet either.
In an interview with Good Morning America, Eichenwald said other Twitter users followed suit, sending him strobing GIFs.
"I don't know of a case where someone has been sued or prosecuted for speech online causing physical harm", he said. "It wasn't the content of the communication that was meant to persuade somebody or make them feel badly about themselves; this was an electronic communication that was created to have a physical effect". The same organization reports that these seizures can be brought on by everything from mandatory strobing fire alarms in public buildings and vehicle emergency lights to television shows and even sunlight flickering through Venetian blinds.