Who killed Iron Wolf Bowden?
There's no other reference to this person in the dialog or other assets in the game that I can find, so I don't think there's an "in-universe" explanation as to who this person is.
However, Nathan Bowden is one of the artists for the game, so it's highly likely that this is an easter egg left by the development team. Nate is also one of the zombies you can fight in Development Hell.