patricia yu, cnn, new york. >> it's called "murder by proxy -- how america went postal."t the mass murders at work including a 1 the 1 massacre at a post office. a disgruntled worker returned to work and shot four before he killed himself. >> on a memorial plaque, workers defaced the name of the senior supervisor with red ink. >> when i found out that chris carlisle had been shot, i was sad to say, i was very happy. >> you would hate to say something like that, you wouldn't want to think that way because you don't want to wish anybody dead, especially over their job, but there was just an overwhelming sense of relief some of those people were gone. >> it's complicated. yes, i think it's terrible what he did. he killed five people. several more are physically disabled for the rest of their lives. he took mothers away from their children. he took fathers a i way from their children. on the other hand, i understand why he did it. >> anybody ever knew about abusiveness, it happened at that post office. 1987, the same managers allowed up in royal oak did the same thing in indi