Maybe it has to do with barometric pressure changes combined with maybe something in the air or something frequency related? With the seizures and strokes it makes me think they could be sending out some sort of frequencies affecting certain people's brain waves.

Did all of them have the same cell phone carriers, cable or satellite carriers, or new smart meters?

Were they in rooms with TVs on when it happened? I've seen other threads on here about how people have had weird reactions to TV lately.