U.N . Ambassador Susan Rice recalls stepping over bodies in Rwanda . United Nations staff recalls 1994 mass killings in Rwanda . Ban encouraged the world community to remember its shared duty to prevent future catastrophes in the name of humanity and in honor of the memory of those who died . Obama says tragedy will always be remembered .
U.N . Ambassador Susan Rice recalls stepping over bodies in Rwanda . United Nations staff recalls 1994 mass killings in Rwanda . Obama says tragedy will always be remembered .