Nope. I don't even know what the fire button is because it was firing even if as I started the game before I touched a button.
The fire button is either the space bar (or enter) on keyboard or the A/B button on gamepad (you can check the README.txt file). It might be that the space bar or one of the buttons is stuck? Do you have a gamepad connected to your PC while playing?
No, not at the time. I did not know it was supported. I'll try it again another time.