Engine won't stop

I have a Briggs 190412-3098-01 880122110. The engine was running but not good. The carburetor needs some work on it. I pushed the metal tab onto the spark plug to shut it down and the engine kept running. I pulled the spark plug wire off and it kept running. I had the plug wire about 3 inches from the plug and could not see a spark jumping the gap. I finaly choked the engine off. Why is the engine running with the plug wire off? Thanks for any help.

something inside the cylinder is glowing red hot and that is what is igniting the fuel.
This is also part of the reason why the engine is running bad.
You will have to take the head off and have a look.
better still take a photo of the piston to & the inside of the head and post them here.