Where The Skeleton Came From
Before making the call, he was stopped by the forensic experts. And it was a good thing what they did. They unpacked their tools and started inspecting the skeleton, where the skeleton came from.
Investigation
It usually takes at least a week for forensic investigators to determine who is left and where or where. They stopped John from calling because what they found was that no further investigation is needed in this case. They had everything they wanted already.