Is it legal for the officer's that are involved in a shooting to put evidence in one of the police car involved and leave the crime scene?

In the video you car see Sgt Murphy (bald headed) put something in the car and Cst Power take out medical kit from car #A22 trunk then turn on emergency light's after backing up car. Is it legal for police to leave the crime scene with a police car that was involved in a shooting? Why were they allowed to do that? is it common for police to remove evidence (car #A22) from crime scene? car #A22 was not returned to scene but replaced with a different car, is that common and legal for police to do? First paragraph below from fatality inquiry states Power and Murphy left the crime scene.