What timelines are you assigning: (1) Officer Baker/Roy Truly arriving at the TSBD 1st floor stairwell, (2) Lovelady/Shelley arriving at the TSBD 1st Floor stairwell, and (3) Adams/Styles arriving at the TSBD 1st Floor?
Adams, Styles, Shelley and Lovelady are in the area near the first floor elevators 50 to 70 seconds after the shooting.
Truly and Baker arrive on the scene 10 to 20 seconds later.
Obviously, these are guesstimates but it's somewhere in this ballpark IMO