According to the DM article in the link, they say he didn’t use a ladder but “clambered up [the] building’s air conditioning system.”
... however looking again at Google Maps, it seems clear the air conditioning units for that building are on the side FACING the arena - so unlikely he ascended that way or he would have been in full view of the SS snipers.
Street View also shows that back in Nov 2023 there was no ladder against the building behind the conifer trees.
I posted about the air conditioner yesterday in another thread and was corrected numerous times by the ladder brigade.