I can't think of anything that will really be a huge help (nothing can replace stolen lives) But I was thinking maybe holding a candle light prayer or something near the scene. Pray for the dead, the wounded and the families... I don't know. It's the only thing that I can think of. At least offer our support? I wish I wasn't in Afghanistan, so I could take part in whatever helpful activities that I could.

EDIT: Maybe bring flowers or "care packages" to the wounded in the hospitals? Maybe start a fund to help with funeral cost?