OK, so technically it may not be 'Justifiable Homocide', but I'll bet you agree it's a justifiable homocide, right? (Obviously, assuming the dad was correct and the dead guy did it)
Assuming the dead guy really did it, I'd probably call him guilty on manslaughter, but it would probably depend a lot on the exact penalties he could expect. If the prosecution went bonkers and tried to nail him on first degree murder or nothing I'd probably acquit. Especially if they used the fact that he broke in (homicide committed in the course of a felony) to go for the death penalty.