By Ralph Ellis and Madison Park

CNN

(CNN) -- An additional charge has been filed against a Maryland man accused of tweeting an animated strobe image to a journalist with epilepsy, prosecutors in Texas said Monday.

John Rayne Rivello, 29, was charged with aggravated assault with a deadly weapon, said Brittany Dunn with the Dallas County District Attorney's Office.

A grand jury referral said Rivello sent the tweet knowing journalist Kurt Eichenwald was "susceptible to seizures and that such animations are capable of causing seizures." The document said Rivello used "a deadly weapon, to wit: a tweet and a graphics interchange format (GIF) and an electronic device and hands during the commission of the assault."

Prosecutors said Eichenwald was chosen because Rivello had a bias against people of Jewish descent.

Eichenwald's attorney, Timothy Perkins, told CNN: "We consider the message like a bomb or sending anthrax to someone in the mail."

Federal authorities previously charged Rivello with cyberstalking.

CNN was unable Friday or Monday to reach Rivello or his attorneys.

The flashing image was sent to Eichenwald, a Newsweek senior writer and Vanity Fair contributing editor, on December 15 and came with the message: "You deserve a seizure for your post," according to the federal criminal complaint. Eichenwald said the image triggered a seizure and he then sought to identify the person who sent it.

"After a 3 month investigation, the FBI this morning arrested the man who assaulted me using a strobe on twitter that triggered a seizure," Eichenwald tweeted last Friday.

The FBI and police in Maryland and Dallas, where Eichenwald resides, investigated the case and arrested Rivello.

Rivello, who is from Salisbury, Maryland, was initially charged with cyberstalking and appeared in federal court Friday.

The Twitter account belonging to Rivello allegedly contained direct messages sent to other users regarding Eichenwald with statements like, "I hope this sends him into a seizure," "Spammed this at (victim) let's see if he dies," and "I know he has epilepsy," according to the allegations in an affidavit that was unsealed Friday.

Investigators also found screen shots from an epilepsy website with a list of commonly reported epilepsy seizure triggers and a story from a Dallas news site about Eichenwald's efforts to subpoena Twitter to track down the user who sent him the image, according to the affidavit.

Since the first incident, "More than 40 ppl sent strobes once they found out they could trigger seizures," Eichenwald tweeted. "Stop sending them," he wrote.

He said identifying information about the people who sent him those strobe images is now "currently in the hands of the FBI."

Eichenwald has been public about having epilepsy. In October, he wrote in Newsweek that one of President Donald Trump's supporters with the handle "Mike's Deplorable AF" had tweeted to him after he had written about Trump's conflicts of interest.

"Mike" mentioned his seizures and sent him a video of strobe lights.

"It's what's called epileptogenic -- something that triggers seizures. Fortunately, since I was standing, I simply dropped my iPad to the ground the second I realized what Mike had done. It landed face down on the bathroom floor," he wrote in Newsweek.

Not all people with epilepsy are photo-sensitive. The Epilepsy Foundation estimates that certain visual patterns and flashing lights can trigger seizures in about 3% of people with epilepsy.

"When people have photosensitivity, it's reduced by taking medication, but it's not obliterated by medication," said Dr. Kimford Meador, a professor of neurology at Stanford University Medical Center. "The risk of it is markedly reduced if they're on medication, but patients try to avoid situations where they have flashing lights."

CNN's Tony Marco contributed to this report.