Is this a seizure?

It certainly sounds like a seizure. He should consult with a doctor. I have seen a study that infers that modern cannabis is much stronger than it was years ago and could possibly cause seizures. I also saw a conversation thread where someone said their spouse had smoked pot for 30+ years, but started having seizures. Because of the seizures, he stopped smoking which seemed to stop the seizures.

Your friend still should go to a doctor to make sure nothing else is going on.