A Twitter message that caused a Dallas journalist with epilepsy to suffer a seizure led to assault charges against a Maryland man on Tuesday. It also exposed a terrifying way people with epilepsy can be attacked online.

John Rayne Rivello, 29, of Salisbury, Maryland, was charged with aggravated assault with a deadly weapon, which carries a hate-crime enhancement, The Dallas Morning News reported. He was booked at a Dallas jail Monday night and has been released on bond.

The Dallas grand jury said Rivello “knowingly and recklessly caused bodily injury to Kurt Eichenwald, a disabled person, ... by inducing a seizure with an animated strobe image, knowing that the complainant was susceptible to seizures and that such animations are capable of causing seizures,” according to indictment documents shared by Eichenwald, a Newsweek political reporter who has written about his epilepsy.

The grand jury said Rivello’s “deadly weapon” included a tweet, a GIF image and an electronic device.

The GIF reportedly included the statement, “You deserve a seizure for your post.” When Eichenwald viewed the tweet, he suffered a seizure. Eichenwald’s lawyer told The New York Times that Eichenwald was incapacitated for days, lost feeling in his hand and had trouble speaking for several weeks.

Last night, for the second time, a deplorable aware I have epilepsy tweeted a strobe at me with the message "you deserve a seizure' on it... — Kurt Eichenwald (@kurteichenwald) December 16, 2016

The next day, Eichenwald tweeted about the strobing message and said he would take legal action against the person who sent it.

He told “GMA” that his wife captured a still image from the seizure-triggering animation. GMA shared the still version on air, which appears at 2:38 in the video below.

According to the affidavit, Rivello’s Twitter account contained direct messages written by Rivello that included statements including, “I hope this sends him into a seizure,” “Spammed this at [victim] let’s see if he dies,” and “I know he has epilepsy,” the Department of Justice said in the statement.

The FBI arrested Rivello on Friday after its investigation, the agency said in a statement.

Steven Lieberman, Eichenwald’s attorney, compared the online attack to someone sending a bomb or anthrax in the mail.

“It wasn’t the content of the communication that was intended to persuade somebody or make them feel badly about themselves,” Lieberman told Newsweek. “This was an electronic communication that was designed to have a physical effect.”

Eichenwald said Friday that more than 40 people have sent him strobing images knowing they could affect his epilepsy and trigger a seizure. He said that their “identifying information” was with the FBI.

After a 3 month investigation, the FBI this morning arrested the man who assaulted me using a strobe on twitter that triggered a seizure. — Kurt Eichenwald (@kurteichenwald) March 17, 2017

He currently faces federal charges & is expected to also be indicted by the Dallas District Attorney on different charges in next few days. — Kurt Eichenwald (@kurteichenwald) March 17, 2017

Identifying information about every person who sent me strobes after finding out about the assault is currently in the hands of the FBI. — Kurt Eichenwald (@kurteichenwald) March 17, 2017

Eichenwald’s case is different from other online stalking or bullying lawsuits because the tweet Eichenwald received wasn’t just sent to harm him emotionally, it was designed to target his medical condition, The New York Times pointed out in a report. The attack was also completed in a relatively simple way.

Vivek Krishnamurthy, an assistant director at Harvard Law School’s Cyber Clinic, told the Times that while some online attacks are aimed at affecting an electrical grid or gain control of air traffic controls, Eichenwald’s attack was “distinguishable because it is a targeted physical attack that was personal, using a plain-Jane tool.”

Richard Spencer, a white nationalist who is credited with coining the term “alt-right,” called Rivello a “hero of the meme war” and proposed to start a legal fund for the suspect.

Epilepsy is a brain disorder that causes recurring seizures which could also lead to violent muscle spasms and loss of consciousness. According to the Epilepsy Foundation in Michigan, 1 percent of Americans suffer from the disorder.

A similar cyberattack targeted a group of epilepsy patients nearly a decade ago. In 2008, the hackers posted a number of strobing images to a support message board on the Epilepsy Foundation website, triggering headaches and seizures in “a handful” of epilepsy patients.