The fact that one would even ask such a question signifies to me that an abundance of training is needed.
No, not self defense trainging per se, but general gun safety and legal.
You need to always identify your target. Just because there is the sound of breaking glass does not signify that a crime is being committed. When you use a firearm for self defense you are not given "second chances" so to speak. Therefore it is most important that you be right 100% of the time.
If you can't identify your target, how do you know it's a threat?