This song, as heard at the death scene of "William Shakespeare's Romeo + Juliet", is a piece from Richard Wagner's famous "Tristan und Isolde."
I don't know exactly how to describe it, but I can tell you this:
A few years ago, after studying Shakespeare's tragedy "Romeo and Juliet" and watching Baz Luhrmann's version of the film, young student Kip Kinkel became obsessed with what is often called "the greatest love story ever told." Kip believed that "Romeo and Juliet" was exceptionally relevant to his own life. He had recently been a victim of unrequieted love and he felt his parents' constnat pull over him. One day, Kip had a psychotic break. He carried a gun to school and shot several of his classmates, killing them or leaving them seriously injured. He ran. As his parents arrived back at home, Kip blasted "Liebestod" on his stereo, took up his gun, and shot and killed both of them. The music was still playing loud and clear when the police arrived at his home to arrest him.
Scarily enough, that is how moving this music really is.