...uh...if Reeves shot himself in the head...wouldn’t that make him the shooter?
...stirring slowly...he, he, he...
Yeah, he likely murdered them all, however, there is always a chance he didn't. Trust me, stranger things have happened and this is delayed until all the evidence tells them that.
Simply put, until their investigation is completed, they won't definitively tell ya who the murderer was and or what the likely motive was.
I personally am more interested in the motive.