I did some googling. It appears there is a suspect that was named in Dec 2007 but so far nobody has been charged. A man by the name of Preston Strong is suspected of killing a Yuma DR. There are similarities between the 2 crimes. Strong has been in jail for theft charges. He appeared to be a well known con man. He also new Luis Rios, the boyfriend of the mother and children who were all killed.
http://media.yumasun.com/multimedia/YPDRelease_PrestonStrong.pdf
http://media.yumasun.com/multimedia/YPDRelease_PrestonStrong.pdf