Some surreptitious fiddling with the screwdriver in this photo revealed that it was being used to "dog open" the door - hold the latch retracted so the door was free-swinging. This was probably an ingenious, although not appropriate, way to fix a door that was not meeting the "this door to remain unlocked during buisness hours" code. Becasue it could be so easily tampered with (as I did myself) it is not a good way to fix one of the main egress doors on this retail buisness.
Check out the following links for more information on how to fix exit devices appropriately: http://www.hagerco.com/DocumentationIndex.aspx.