...intending to commit a forcible felony (kidnapping your wife/kids, assaulting your children, murdering you), especially if you discover them in the home.
In the scenario you've described, I hope I never have to determine what I'd really do, but my guess is that I would calmly tell them to get on the ground. If they made any movements other than towards the ground, I'd probably shoot them (for fear that they were about to commit a forcible felony on my personal property, and I would be defending myself and my family members).