Mrs Garner was on the 4th floor by the rear staircase and saw Baker/Truly coming up using the staircase =
Encounter on 4th floor improbable
On 3rd floor , if the shooter from 6th floor is the man encountered, would require the west elevator to be used to bypass Mrs Garner without being seen by Garner.
west elevator used by the 6th floor gunman, would require an accomplice who could take the elevator back to the 5th floor by not later than approx 70secs post shots.
If using the west elevator and getting off on the 3rd floor, the gunman would have arrived there by 40sec post shots, so it’s doubtful any encounter with Baker/Truly would have been probable UNLESS: The shooter hears Adams and Styles whom at 40 sec post shots are just crossing the 3rd floor landing!!!
Having to wait until no longer hearing A&S on the staircase = approx 60 sec post shots= Shooter arriving to 2nd floor landing approx 70-75 sec , hearing Truly shout up and so the shooter diverts to the 2nd floor lunchroom 80 sec post shots and was somehow still spotted by Baker aortic 85 sev post shots.
Note: it’s not improbable the shooter could have taken east elevator all the way to 2nd floor exiting there by 55 sec post shots and then was spotted by Baker because the shooter had just exited the lunch room, and he was actually coming down the 1st half of the 1st floor staircase at 75 sec post shots when Truly shouted.