The answer is:
The man is a psychopath. He sees the girl but the opportunity to contact her never materializes. Yet in the obsession to meet her again he murders his sister with the hope that the young woman will show up at his sister's funeral. The man is a psychopath so everything is just and object for his pleasure. He has no emotional attachment to his sister so when she could help solve his obsession with this young woman by her death she was killed.
This scenerio actually happened.
They asked diagnosed psychopathic criminals the same question I originally asked. 100% answered correctly! All psychopaths think alike.
When they asked the general population the same question, approximately 25% got it right. Most police detectives got it right, because they begin thinking like criminals in order to catch criminals.
Now PHO127, asks how do I know he isn't a psychopath. Well, since only about 1% of the population are hard core psychopaths and about 10% of the population have some psychopathic tendencies we may safely assume that PH0127 has about one chance in a hundred to be a psychopath and one chance in ten to have some noticable psychopathic tendencies just like the rest of us.
How do I distinguish. One you aren't in prison (I hope) and you have no history of psychopathic behavior (I hope). So I am assuming you have worked in law enforcement or you are just a little quirky.
Keith