Let's consider the defender's primary goals:
- Avoid getting shot
- Prevent others in the household from getting shot
- Avoid injury to innocent third parties
- Minimize the liklihood of having shots occur
Engaging and shooting a "bad guy" should
not be among them unless it becomes necessary to do that to meet Numbers One and Two, and unless of his accomplices should be able, and choose, to leave after you have shot the first one, it would not be sufficient to do so. The objective is
not to "control a battle."
If the defender fails to achieve Objective Number One, the attainment of Objective No. Two will be at risk.
Fulfilling Objective Number Four will go a long way toward meeting the others.
Only an assassin--someone with the objective of killing the family members--would want to
knowingly break into a safe room; he would put himself at extreme risk; and be sure of success, he would likely have to use smoke or explosive devices.
On the other hand, one would reasonably expect any burglar to shoot for his own self preservation if he sees someone aiming a firearm at him.
Every single trainer, instructor, and expert of whom I am aware recommends getting the family into a safe room and defending from there.