Gamma core device possible side effect?

I took my son (25yrs. old) to the neurologist this past Monday for a check up and med review. While there the dr. decided to try this device on him stating that it would either help or not. If it helped he would get us the paperwork needed to get one. My son was seated on the exam table and the nurse put 30 seconds on the device and put some gel on the device and put it to my sons neck/jawline. He stated that it felt really weird and asked could they do it with him laying down. The nurse went and asked the dr. and came back into the room and said yes he could. He had just laid down, stated he felt weird then his whole body seized up, eyes rolled back in his head and was unresponsive for approximately 1 to 2 mins. He finally responded to me for mabey 1 min. then started to seize up again with eyes rolling back and unresponsive for another minute or two. He had never had a seizure before.

The squad was called and we were sent to the ER. They drew blood, did ct scan and gave him fluid but came back with no answers as to what happened. His neurologist said anxiety attack but my son says absolutely NOT!!!! He has had panic attacks before and this wasn’t even close. He said he was coming in and out of consciousness, and felt like he was dying. Soooo I am writing this in hopes that someone might have answers or helpful information as to what happened????? Everything I read about this device is that it’s completely safe and non evasive. Going to a neurologist ASAP for an EEG but need answers as to what happened. No one seems to know.