What might have killed him?

So I am studying my micro book, and came across a case study.  I am hoping a T.A may be able to assist me in answering the 4 questions.

The case study is as follows:

In the summer of 1999 you are working as  a triage nurse in the Emergency department of a hospital.  A young-athletic man in his early 20's is helped into the hospital by his girlfriend.  He greets you and sits down, but is feverish and his breathing is labored.  The girlfriend answers your questions for you.  She says the symptoms began about 24 hours ago and seemed to worsen quickly.  After listening to his chest you decide it may be pneumonia.  You return him to the waiting room until an examination room is free.

45 minutes later the girlfriend starts screaming, "I think he's choking."  You and the attending physician arrive and he is suffering from acute respiratory distress.  Later that same evening the patient dies.  Lab work reveals that the cause of the death was not bacterial.  No other cases of this type are reported for the summer.

1. What might have killed him? (list)
2. What other facts might you have required to try and determine the nature of the infection?
3. Describe the transmission characteristics of suspected agent?
4. Why might it have been a poor idea to send the patient back to the waiting room?