I just posted this on a different thread, but I'm going to post it here too.
Here's one of the pictures at your link.
In front of the alley where the ladder is located, there are four bushes/trees. The color of the ground in front of those trees is different from the color of the rest of the ground there. Could this indicate that those trees were recently planted there for some nefarious reason?
It seems like an odd grouping of trees, and it also seems like an odd place to put trees, in front of an alley like that. Take a look at it, and see what you think.
From what I understand Crook used his ladder to easily access the roof of the building. The cops that went up to see about a gunman on the roof, used the stationary ladder, and as one cop hung on to the edge of the roof, unable to draw his weapon, Crook backed him down with his shotgun.
So they’re very well could have been two ladders.