There is no lesson. There is no good that comes from this evil. Yes, God can bring a good out of any situation but this can almost sound like God had a part in this and He surely did not. He allows it and we can be angry that horror floats over our blue planet daily.
For some reason this murder of these bright eyed children haunted me for many days. Was it because I have a bright eyed child of six years of age? I'm not sure. I kept hearing a whisper in the wind saying in a hushed voice..."the horror...the horror."
My wife and I did hold our sweet child more often for several days. The only way to even see a small glimpse of God is to "look for the healers."