Using dry fire drills from www.mattburkett.com and I guess I forgot to unload my weapon.
I kid, I kid. Looking at the web site gave me the idea of putting a couple of bullet holes on the screen.
Remember the 4 rules of gun safety:
1. All guns are ALWAYS loaded.
2. Never point a gun at anything your not willing to destroy.
3. Keep your finger off the trigger until you're ready to fire.
4. Be absolutely sure of your target and whats behind it.