In Minnesota, much criminal investigative data is confidential or protected nonpublic while the investigation is active. There are a few exceptions to this, but not many. (See subd. 7 of the statue linked.) The questions answered during the press conference fit the exceptions.
The investigation will likely remain in active status until the trial or conviction.
MOO: I'm wondering if they also might be preparing to present evidence to a Grand Jury to help determine which charges or what level of charges to bring forward. For example, premeditation.