The Epilepsy Foundation has filed a formal criminal complaint over a series of attacks that transpired on its Twitter feed in November when someone apparently tried to trigger seizures by showing flashing and strobing lights.

The attackers used the Foundation’s Twitter handle and hashtags to post GIFs and videos containing flashing lights and strobing effects, which in some cases can cause a person with epilepsy to suffer a seizure. The attacks took place during National Epilepsy Awareness Month when a larger than normal number of people were likely following the feed.

“These attacks are no different than a person carrying a strobe light into a convention of people with epilepsy and seizures, with the intention of inducing seizures and thereby causing significant harm to the participants. The fact that these attacks came during National Epilepsy Awareness Month only highlights their reprehensible nature,” said Jacqueline French, M.D., chief medical and innovation officer of the Epilepsy Foundation and professor of Neurology at NYU Langone Health’s Comprehensive Epilepsy Center.

About three percent of the epileptic population are sensitive and potentially triggered by this type of lighting.

“While the population of those with photosensitive epilepsy is small, the impact can be quite serious. Many are not even aware they have photosensitivity until they have a seizure,” French said.