1994 Other Saturn Models engine shuts off when I press on Br

Electrical problem
1994 Other Saturn Models Two Wheel Drive Automatic 107000 miles

How do I find problem here.
My Car had a transmission leak. Filter which is located in front of transmission leaked out 3 qts of oil.
I replaced filter and fluid

The car will now shut off when I press on the brake.
It will also drop in RPM if I put on signal lights.
If I put on hazard lights it also drops in RPM

How do I find the source of this problem
Today for 3 hours the car ran fine but this evening when I pressed the brake pedal the car shut off.
And each time I start the car not if I press the brake pedal the engine will shut off.