This article gives the COD in the title, and in the article itself. It sounds like only one gun shot wound in the head from this article.
Police: Gianni Belvedere shot in head
http://www.utsandiego.com/news/2014/feb/07/gianni-belvedere-autopsy-findings-released/
"Homicide victim Gianni Belvedere, whose decomposing body was found in the trunk of a car in Riverside last month, died from a gunshot wound to the head, San Diego police said Friday."
Not to be totally morbid but I can see where "gunshot wound to the head" as COD could be one shot or more than one. Most likely one shot killed him, but there could've been more shots. Wow did it make me sick to type that.
I'm still reeling over the fact that Ilona was potentially so close to being rescued too.
I hope the people who did this are found.