The plice say they know the motive for the killing, and that is why Hacking was arrested for aggravated murder. However they hadn't talked to the DA's office, so...
They could have unreleased evidence of aggrevating circumstances, or they could be trying to encourage plea negotiations.
In a case with this high of a profile, I would be highly surprised if the police were not consulting with the DAs office at each step. Is there a history of bad relationships between the DA and the cops?