Hackers broke into the Epilepsy Foundation’s Twitter feed last month to post images of flashing or strobing lights known to cause seizures, the organization has confirmed.

The attacks deliberately targeted the Epilepsy Foundation’s Twitter feed during National Epilepsy Awareness Month, a time period when the most people with epilepsy and seizure disorders would have been following the account, according to the organization.

Through the Epilepsy Foundation’s Twitter handle, attackers posted images and GIFs that flashed seizure-inducing lights. The nature of the attacks is similar to an incident in 2016, when the journalist Kurt Eichenwald, who has epilepsy, was sent a tweet with a strobing GIF that triggered an immediate seizure. The message sent to Eichenwald, who had been subject to several online attacks for his coverage of President Donald Trump’s campaign, read: “You deserve a seizure for your postings.”

According the Epilepsy Foundation, exposure to flashing lights or certain visual patterns can trigger seizures in about 3% of people who have epilepsy.

“While the population of those with photosensitive epilepsy is small, the impact can be quite serious,” Jacqueline French, chief medical and innovation officer of the Epilepsy Foundation, said in a statement. “Many are not even aware they have photosensitivity until they have a seizure.”

The foundation has now filed criminal complaints and intends to cooperate with law enforcement to “ensure that those responsible are held fully accountable.”

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Write to Mahita Gajanan at mahita.gajanan@time.com.