Active Crime Scene
A crime scene that is still giving off evidence and has not yet been completely processed and cleaned. A single Officer-in-charge is responsible for coordinating investigation at the scene. Unauthorized people (including witnesses) must be excluded from an active crime scene.
http://www2.cruzio.com/~zdino/psychology/criminal.justice.glossary.htm
Once the crime scene has been processed and released they relinquish control/possession back to the owners. Once the crime scene has been processed and released, law enforcement doesn't restrict who enters the scene.
They can delay the release of the scene if they feel they need to, get a court order to keep it in their control. Certainly would have been granted in this extreme case.
That scene is now out of LE's hands and in the hands of Mandalay Bay, who owns it. LE cannot restrict movement, seal it, r say who goes in or out now that it's released.