A few observations:
1. Reasons for taking Jo Ann off of the Amber Alert - either she was killed or it was determined she is playing an active role in this.
2. The bodies in the back yard that have yet to be identified - it's very possible they have been there for weeks, months or years and hence the need to use buckets and sift the back yard.
3. What was the trigger? Obviously, AM had full 100% access to these kids seemingly unsupervised. The plan was for he and GB to drive to AZ. It would have been much easier to rid the family of GB during their trip alone, feign a 'disappearance' along the way, rather than kidnap 4 people and go on the run. Getting rid of GB would have been the fastest way to a goal of having Jo Ann and the children in his life rather than vice versa.
This is one crazy case....