Richard, some thoughts.
Regarding the Shelley first day statement that claimed he called his wife. Do you believe the call was made and if so when? It would seem that there were various stages that occurred after the shooting. Stage one involved confusion of witnesses, particularly as to the direction of shots. Those employees that did not believe hey came from the building may have ventured back inside in the first few minutes. We know some loitered in the doorway and Mrs Reid claimed to have gone to the 2nd floor.
Within a few minutes Brennan had relayed what he had seen and eventually Sawyer and others mistakenly went to the 4th floor based on his explanation. This would represent stage two. At this time it would be deemed unsafe for employees to be inside given the possibility of a shooter still present. We see some of them outside and police at the front door. We see Lovelady outside at this time. Perhaps Shelley is assisting police inside at this time as he claimed.
At a later time, around the time Sorrels arrives (1pm) employee details are taken. The SN and gun are discovered by 1.20 pm and Fritz tells Stenkel to gather all those who worked on the sixth floor and take them for questioning. Somehow Frazier has been allowed to leave by this time.
If Shelley made the call I believe it would have been in stage one. After that the phones would have likely been commandeered by police/press and he would have been occupied assisting police or on his way for questioning.