Steven Krantz tells the following story, Mathematical Apochrypha, page 136:
My Ph.D. thesis was based in part on work of Walter Koppelman of the University of Pennsylvania. My source was a very brief research announcement that Koppelman had published in the Bulletin of the AMS. I could never find the promised subsequent paper that would fill in all the details, and I had to fill them in myself. I eventually went to my thesis advisor and asked him where the missing paper was. He said, "Oh, God. Don't you know?" And then he told me the sad story. There was a very unhappy graduate student at the University of Pennsylvania. He had had bad experiences with several thesis advisors (at least so he thought), the last being Koppelman. One day he went into the colloquium, shot the department chairman, shot Koppelman, and shot himself. Koppelman and the student died.