Look, guys, as I said on the other thread about this, I've had lots of experiences having to attend scenes where there were dead bodies, mainly called "sudden deaths".
And believe me, after less than a week dead, it wouldn't matter that you'd never spoken to that neighbour for yonks, you'd be absolutely bowled over by the smell coming from the place. It reeks to the high heavens. How anyone can not know?
You'd have to be Michael Jackson wearing the face mask. Bet he pongs a bit now!