Macho,
Filter everything !!!
Be quick !!
If have another tank put half of the fish to that with fresh water and just Oxygen Filter.
Do not put anything else.
Do the same to the original tank as well. Keep the other half of the fish in it.
Macho :)
Is your vehicle a car or a van ??
I have seen this problem and had an experience as well.
It has come to the A/C air intake.
As air sucks in debri / leaves /water too do get into this chamber. But the intake is open at the bottom as well to let water to drain.
In some instances...