Incident that Inspired this Film
During the December 2011 podcast of "The Projection Booth" re "Electra Glide in Blue", the screenwriters of the film indicated that the film was based on an incident where an Arizona motorcyle patrolman was shot off his motorcyle and killed by a man shooting from the back window of a camper. This tragic murder became the seed for the film, and the source of the stunning end sequence of "Electra Glide in Blue".
FYI, I found a description of the real incident, which occured on December 28, 1970. The murdered Officer was motorcycle patrolman Albert Bluhm. The confessed killer was James D. Parle. Link to the case summary below:
http://az.findacase.com/research/wfrmDocViewer.aspx/xq/fac.19740424_0040300.AZ.htm/qx
Patrolman Albert Bluhm R.I.P.
http://www.odmp.org/officer/1962-police-officer-albert-r-bluhm
Projection Booth Podcast:
http://projection-booth.blogspot.com/2011/12/episode-42-electra-glide-in-blue.html
James D Parle Mugshot
http://mugshots.com/US-Counties/Arizona/Maricopa-County-AZ/James-D-Parle.4681316/details/