I thought it might be interesting to look at what poems have been written about this event. I found this interesting reference to a poem, and of course many poems written by children. One of my favorite poems about death is "Stopping by the Woods on a Snowy Evening" but even that does not seem appropriate here.
Emily Dickinson's "I Measure Every Grief I Meet" speaks to the sorrow and tragic circumstances of the Connecticut shooting.
I really like the above post's suggesstion about "In Guernica." Read the poem and then go and look at Pablo Picasso's famous painting "Guernica" about the same devastating bombing.
A poem, in the form of musical lyrics, that speaks to the themes of the massacre in Connecticut is "In Guernica" by Joan Baez. It is not directly about the Connecticut massacre, but the sentiments expressed are essentially the same.
The opening line expresses the Guernica tragedy (and in effect, others) with understated power:
In Guernica the dead children were layed out in order on the sidewalk
In their white starched dresses
Guernica was bombed in 1937 by the Nazis. This Basque town was bombarded during the Spanish Civil War. The killing of innocent children in this poem/song also speaks to me of the killing of the innocent children in Connecticut.
But it should be a famous poem or by a famous poet :))