In the 'Slasher' segment, Paul Bradford is found by the police, in an alley with a dead body. He is arrested, and put in the back of their car. When we next see him, the officers are just calling in the crime, and requesting back-up to the alley - but they are already driving. This means that the officers have simply left the body and the crime scene, without taking any steps to secure it or call it in.
In reality, the officers would have to wait for back-up to arrive before they could leave the scene.