He rented an office to Eldon Frankenstein for a clinical study. The man only saw Eldon once and knew only that Eldon was running a clinical trial with student volunteers.
After the murder of Eileen MacCormack, he was ordered not to let anyone into the office Eldon had worked in. In the guise of FBI agents, hunters Sam and Dean Winchester arrived to investigate the murder and were led to Eldon's office by the building manager. He explained to the Winchesters how the janitor entered after hearing screaming and saw Eldon jump out the window and run off after falling three stories. At Dean's request, he shows the Winchesters the security footage of Eldon jumping to the ground and running off, identifying Eldon as the one who had rented the office to them.
The manager follows Sam's instructions while playing the video and pauses then zooms in on a crest on Eldon's arm. The Winchesters recognize the crest as belonging to the Styne Family and the manager explains that while Eldon had been renting for a month, he only saw him the one time. After the manager states that he didn't know that Eldon's study had to do with eyeballs, Dean jokingly suggests that the manager will ask about it the next time. As Sam is drawn away by a phone call, Dean leaves the manager his card and asks the manager to call them if he thinks of anything else.
After the Winchesters leave, the manager tries to exit the office only to be stopped by Eldon. Recognizing Eldon, the manager nervously backs into the office where Eldon shuts the door and calls him "quite the chatty-patty." Eldon asks what the manager told the Winchesters and he nervously states that he told the Winchesters hardly anything and that he has "nothing to say." Drawing a knife, Eldon stabs the manager in the chest, killing him after which Eldon states "I believe you."