He went into the house prepared. He had a plan. He executed it.
It’s almost, so far, the perfect murder. Not only is he not a suspect, many people still don’t even believe that he exists.

He went into the house prepared. He had a plan.

Even if you believe that he botched his plan in one way or another, he still went into the house prepared for something, he had something in mind, he had a plan. If criminal success can be measured in terms of ‘getting away with it,’ then this crime was a huge success (so far). A fluke? Convergence? or something else… ?

Maybe the killer knew in advance how he was going to gain access to the house?

Maybe he already knew what to expect?

it would seem reasonable, considering thte above that he already knew how and where he was going to enter the house and what risks were involved. after all, he had a plan.