PrintFax is at the far left of the third floor, on the left (west) end of the mall.
It is the owner of PrintFax, who is never seen without his robber's mask and black clothing.
Go left into the west end and check the copiers at PrintFax for clues.
On the copier in PrintFax, select MENU and "reprint last document scanned."
Continue on to the left side of the mall. Gus will suggest you take another look for clues at PrintFax.
After the crash of the dummy, go to the left end of the mall. On the copier in PrintFax, select MENU and "reprint last document scanned."
When the cart wrecks at the fountain, go back to PrintFax. On the copy machine, press MENU to bring up the last image.
Obviously the robber put the dummy into cart to distract you. Go back into the left side of the mall. Gus will suggest that you look at PrintFax for a clue.
After you get the scooter, charge it, and chase the cart into the fountain, head back to PrintFax and click on the first copy machine. Press "menu" and select the last scan.
Click the paper on the desk. This is all Gus needs to put together the clues that point to the owner of PrintFax, who may be involved in all of the strange occurrences.
You don't need a key. When the dummy crashes the cart into the fountain, travel to PrintFax and look at the first copier. The MENU will bring up the last copy that was scanned.
You discover that the guy running PrintFax is also the one leasing the empty store space beneath Slugger's Keepsakes. Gus says the odd disturbances began around the time the lease was signed. Head to PrintFax to investigate (you won't get all the way there).
Go inside? There is a form on the desk that implicates the owner of PrintFax in some of the odd goings-on, and there must have been some reason for him to have a key to Good Deals (above Slugger's Keepsakes) and a lease on the empty store (below Slugger's Keepsakes). Head for PrintFax to question him.