I read your question carefully and I understand your concern. Any seizure of new onset in an adult must be investigated. Seizures can be idiopathic, of an unknown cause, but the older the individual the higher the possibility for it to be related to an identifiable issue like brain tumor, infection etc. So he must have tests like brain imaging, EEG, EKG, and some blood tests for possible metabolic causes. One can not speak as to the dangers as long as we don t know the cause. Also you should speak to your son gently to inquire about the possibility of alcohol or drug use which often turn out to be contributing factors in young individuals. I hope to have been of help.