When showing the view that sharpshooter has he is looking at the left side of the building. McGarretts office is on the right and blocked by trees.
The flashback scenes of Danno shooting Joey Collins are from "...And they Painted Daisies on His Coffin". (#1.5)
Uncredited here, Arthur Hee played Joey in that episode.
Steve McGarrett is away in Chicago for the duration of this episode, but keeps in touch with Danny and Kono via telephone.