I’m no Dr. but Ive seen enough to know that was a seizure. The very first thing that happens is loss of consciousness. Patient comes out of it seconds or so later and has no clue why everyone is looking over them. Dehydration or not...this guy ought to get a cranial MRI to scan for tumors STAT.
I don’t think you know all seizures. No, they don’t all come out of it “seconds later”. Grand mal can be very debilitating taking hours to recover.