Hello Good evening,
Your brother was suffered from seizure
(GTCS) also called epilepsy
It is a brain oriented event and you should consult nearby Neurophysician.
some helpful investigations are:
After these investigation, if disease diagnosed as epilepsy and no other significant disease found then treatment will continue much long over the years.
Patient was in post-ictal
phase, so he was unable to identify surroundings at that time.
It is serious event, go to neurophysician for evaluation and management.