I think you should report it to the FBI:
https://tips.fbi.gov/
I don't like the sound of this one bit.
Agreed. Let them sort out whether it's important or not. Get off of here at once and write down all you can think of concerning this ( times, witnesses, where he might have sprayed, etc. ) that happened no matter how trite it seems. The longer you wait, the more you might forget.
Homeland Security should have a place for people to report something like this. Than I would have left there immediately in case it really was something biological he was spraying.