Interesting situation to say the least.
I think for anyone to have an opinion on this they would need to know the following.
What exactly does 'break in' mean?
Where was this diaper party?
Was this guy drunk or high?
If the doors were locked, the homeowner had every right. If the doors were unlocked, which is possible in this area of town, it becomes subjective. You then need to know what the argument was and how long it lasted. You also need to know if the person who was shoot was drunk or high.