The use of deadly force to protect yourself and others is permitted. However, you must feel that you or someone else is about to be harmed, and the person must be attempting to, or have broken into your home. There is no duty to retreat in Georgia.
Castle Laws are laws that address the use of force when defending one's self inside their home, or on their property. Some states expand this to vehicles, and the person's place of work. Castle Laws generally include: the places where this law applies, the requirements fro use of deadly force, if there is a duty to retreat, the amount of force that maybe used in defending one's self or others. These vary widely from state to state.