Wikipedia can be the perfect environment for the growth of a memorial to the victims, which will strengthen and grow the general Wikipedia effort at the same time.

A Wiki of some kind certainly is ideal for this purpose, but frankly, I'm not sure Wikipedia is it. Certainly there should be extensive coverage of the event, taking advantage of the fact that Wiki lets us update the descriptions of the events as more news comes out, leaving us with an historical record of unique accuracy. I certainly think a list of victims is not out of place either. But I'm really not sure that a "memorial" per se is an appropriate thing to put in an encyclopedia. Encyclopedias describe people, they don't eulogize them. Sure, we should have an article on, say, David Angell, and it should list the shows he produced and mention how he died, but it shouldn't be just ABOUT how he died, and it shouldn't be different from a page on any other television producer--neutral and factual, not reverent.

A memorial should also allow friends and family to say anything, and have those comments left intact. See, for example, the memorial to a friend I put on my own site at http://www.piclab.com/sasha/. It is not at all neutral reportage, because it's not meant to be.