It is a known fact that most murders are commited at night,preferably a stormy night with lightning,more a horror effect...a foggy night is ok also,that's good dramatic effect....and one other thing,the murderer always attacks from behind,mysteriuosly out of nowhere,most of the time right from where you have just looked...sheesh,you should really watch more tv (/sarcasm)
;-)
That's his speculation.