Brake lights on while truck off

So Hurricane Barry rained on us non-stop for almost two days. I woke up Sunday morning to a reflection in the window of taillights in my driveway. I peeked outside and saw that it was my truck. Truck was off and hadn't been driven in two days. Cranked truck brake lights went off. Turned truck off brake lights came back on. I did have some water in the passenger side floorboard which is a first for me but with the amount of rain we had I didn't think too much about it.

I am now thinking that the two incidents are related. I am letting the truck dry out today to see what happens.

In the mean time i pulled the fuse for brake lights just so I don't drain the battery.

Any thoughts?

Its related...
The Third brake light seal is toast so water is leaking in through the hole in the roof where the light mounts. It will leak down behind the headliner, run down the back wall behind the rear seats and flood the floor eventually. This is a common F150 issue.
The other thing that happens when water breaches the seal, is it will short out your lights and activate the Hill Decent which is causing your brake lights to turn on.
You will need a new third brake light assembly and a new seal.

Thanks. now that you mention this the third brake light has been intermittent.

you can find them on Amazon or pay the dealer $300+

Ford AL3Z-13A613-G Regular Lamp Assy - Side Marker

Thanks bud, I ordered yesterday. Hurt my wallet a bit...288 total including tax for a brake light seemed steep. Also Barry damaged my roof so I had it repaired for $1000

I'd rather spend that money on performance/suspension parts.

My third brake light leaked and did this same thing. Best of luck to you out there, stay dry.