I think you should take him to a doctor definitely.
There are many possible causes of his fainting
. As you said, it may be a seizure
. And in that situation, earlier he gets to a hospital, the better. Then we can do an eeg for him. If you delay it, eeg may be negative despite it being an actual seizure.
There is also the possibility that this is a TIA
, or a brief stroke
. In that case his medicines may need to be readjusted.
There are other cardiac conditions also that need to be confirmed such as Atrial Fibrillation
I definitely would think that he should be examined by a neurologist