How do you know that NB wasn't trying to make his way into the hall towards the front door,because according to MOST of the newspapers that day,NB had been found in the hall ??
In which case when police made their calculations regarding the body of a female seen through the window,NB ( a male ) wouldn't have been seen if he'd been in the hall.
It'll never be clear nor truthful how or where the three adult bodies had been found because of the amount of anomalies there are in the case as a whole. There's only speculation.