Genuinely, what is your source that he had 'the wrong floor'?

To have 'the wrong floor' implies there was a 'correct floor', which implies either a premeditated set person or set of persons as a target, or a known location associated with some kind of organization or something.

If it was a random 'just hurt people' type of mass shooting, there cannot really be a 'wrong floor', beyond maybe a comparison between overall target rich snd target sparse environments...

Or perhaps it was 'the wrong floor' in the sense of 'the correct floor' being one that worked with some kind of egress, escape plan?

Seriously, what do you mean by 'the wrong floor?'