Presumably, the police would watch the tapes ... which contain a complete explanation of the mirror's history, powers, victims, footage of plants wilting rapidly in its presence, and the hypnotised behaviour of the brother and sister.
I'm not sure how you'd do Oculus 2 after that. A prequel would be dull.
The tapes show a lady totally off her rocker with an odd conspiracy theory followed by her and Tim rearranging the cameras and plants followed by Tim killing her. The only thing we don't know is what the camera shows in terms of what happened to the dog. Most likely it'll show that Tim released it.
One interesting aspect is that the mirror would be put in the police evidence room. Oculus 2 could have some real fun with that, particularly if the courthouse holding cells while Tim is on trial are also in the police station. Let him holler about My Mirror, My Precious!