It is not justified. Where's the evidence this person will keep killing?
To be honest, I think it might possibly be the third option. I hope this helps.
...ok...so...what we do is.
Answer:
Archibald Craven is the master of Misselthwaite Manor and Mary's guardian when her parents die, since he is Mary's uncle. Archibald is also the father of our other main character, Colin Craven. And while Archibald is not necessary a bad guy, he has caused a lot of trouble in his time with his deep neglect of Colin.
Explanation: