Right, that's one really big question answered, although it still leaves us with wondering if the person who River killed was the Doctor, and did we see that at the start of this series?
Even if that's the case, it doesn't explain exactly who she killed, since I don't think the Doctor can be killed as the current Doctor for dramatic reasons, since it would mean that the Doctor could never regenerate again, which would be a bit of a git for continuing the series!