Engine cutting off when brake/clutch pedal released

I have a Murray riding mower model 46503X8.

I depress the clutch brake pedal to start the engine. The engine starts easily and runs when the brake/clutch switch is depressed.

If I release the brake/clutch switch the engine shuts down. I replaced the brake /clutch switch and the pto switch, but the problem did not go away.

I did the following test. With the engine running and the brake /clutch switch depress, I engaged the cutting blades (pto switch) and the engine shuts down.

I have an electrical diagram but need help to solve this problem.