Is there anything wrong with my car?

I have a 2008 Ford Fiesta ST500. I d parked my car on a hill and put it in gear (as I always do in case the handbrake fails). As I returned to my car, I put my foot on the clutch, took the handbrake off so the car started rolling and I tried turning the key to start the engine but the steering lock was on but I d already lifted up my clutch. The car jolted as if it was trying to jump start then there was a loud bang and smoke appeared coming from under the bonnet. I tried starting the car again but the engine just ticked over and wouldn t start. I tried it again after a few minutes and applied the accelerator and the car started. Ever since the car has seemed to lack some power. I'm not sure if this is actually the case or that I'm just paranoid. Anyone got any ideas on what the bang was and where exactly the smoke came from?

I think the bang was the engine as it was trying to be push started with the key off. Pretty sure you didn't hurt anything.