I’m not sure I have all the details here but this is what it looks like. Son commits murder, gets caught, tried, banged up. Parents begin to receive deaths threats, so move home. Local police force knows all about this. Prowler reported around new home of parents. Parents later found murdered.

Central to the investigation will be two telephone calls between Mrs
Stirland, 53, and Nottinghamshire police on the day she and her
husband, 55, died. The second conversation took place minutes before
they were murdered. Local police from the Lincolnshire force took seven
hours to respond.

Were they all off at race sensitivity training? Studying videos of politician’s speeches?