I don't think DS2 is ready to learn about such things from a receptive language standpoint, if nothing else. DS6 has known for 2-3 years now about what happened, which extended at one point to watching a PBS TV program with us that featured video recordings from the day itself. We spent some time talking about terrorists, what motivates them, how they operate, etc. He seems to have a level head about the subject. He was happy to learn that Osama bin Laden had been killed, though he tends to view death as a sad event.
