An Assassin's Diary was a really nasty book, but you do get a sense of the person who is writing it. Bremer was obsessed with the idea of fame. He was aware of the news broadcasts all over the world and was trying to time the assassination to hit the early evening news in the States and the late night in Europe to get maximum coverage.
To clear up some confusion over whether this song is about the assassination of Wallace or Kennedy, Gabriel stated in the introduction to the song during his concert at the Paramount Theatre, Seattle, 10 August 1983, that the song is “partly taken from the writings of Arthur Bremer and The Diary of an Assassin and mixed with a few images of Dallas twenty years ago”
The musical transition reflects the progress and emotions throughout the story. It starts off as a slow, understated piece, where the killer goes through his plan. It transitions twice; first to full-blooded rock for the building suspense, as the target unwittingly comes closer to the assassin; and then back to a quiet, mournful climax as the shooter, having just shot his target, remembers his childhood loneliness and thirst for attention that led him to where he now is.