Horn honks when engine is turned off-not fob left in car???

[Tony1Leo]

Every few days, my horn will honk 3 times as soon as I turn the engine off. The same quick 3 honks as if you left the fob in the car on exit, but within 2 or 3 seconds after hitting the stop engine button. Doors are still closed, windows are up. Can't figure it out. Has anyone else had this problem and know the fix? 2017 grand sport dual shift automatic.

 

[MacMulkin Chevrolet]

The key is still within 5 feet of the car so the key is still being recognized.