Powder bomb coats interior...

So heading to lunch when I start my car to my amazement a white powdery substance pours out of the vents. When I say pour I mean pour. It coated the entire interior. The pic I have attached is from the 2 small (actually 1 since 1 was closed) rear vents, so you can imaging what the front looked like. I actually had to abandon ship it was blowing so thick. No smell to the powder, can't figure it out...not brave enough to taste it. Kinda thicker powder like "Fun Dip" if you guys know what I mean. I think the AC was on recirc (cabin filter is bypassed?), and the car drove to work OK but I think the AC was off. I can find no concentration of a powdery substance on the outside of the car, cowl or otherwise.

Questions:

If on recirc, where is the air intake inside the car?
If on fresh air, where is the intake outside the car?

I would not put it past my kids or co-workers to plant some sort of "powder bomb" near an intake of some sort...but I'm stumped.

BTW I changed the cabin filter just now and there was NO powder on it at all.