This is two years too late, but here goes:
It's taken from "Il Trovatore", an opera by Verdi that parallels Grumpy Old Men in that in features two men fighting over the same woman. The aria is from Act I and is called "Deserto sulla terra", which means "Alone on this earth", which is appropriate given what's happened at that point in the movie. The lyrics roughly translate in English to:

Alone on this earth,
the darkness will comfort me.
I dream to be able to die with you,
it's always a thrill to dance in the instant of light.
A sad fate has joined me to you,
opposed along eternity.
I dream to be able to die with you,
it's always a thrill to dance in the instant of light
it's always a thrill, a sweet thrill
of peace.