[@Oblivion666] given the circumstance how could anyone be mad? 
Concerning the dog; coulda happened in your own back yard. Bad lucks bad luck so try not to beat yourself up too bad.
As for the sister? I'm.. At a loss, actually. The thought of losing my brother was all too real for me a short time ago. Bad car accident. 
The only thing I can say here, and I pray its not harsh sounding, is to make peace with the end you cannot stop. Love your sister every day and make sure her time is pleasant in every way.. 
I'm sorry, man. Truly. Nobody should suffer this.