Because the "case" statement has the annoying feature that after it executes, it "falls through" to the next case statement. (So it isn't just a giant if-else-else structure.) Put a "break" statement at the end of each of those cases, otherwise execution will just continue executing each of the cases down to the last one.
It's amazing how many switch-case structures I have written where I forget to put "break" after every single "case". That's probably why I try to avoid using it.
[Edit: Ouch! Not even second!
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