In PA, Its almost the same, with Paramedic services working with a “Command Hospital”.
If we had a cardiac arrest,the EKG would be sent to the Hospital and the Doc would consult with the crew. But we would work an arrest all the way to the hospital unless it was very clear the person was dead. If it was a witnessed arrest, then it would be worked all the way.
There was a witness interviewed later, but I don’t know whether he presented to provide down time during the incident. UCLA’s ER is roughly 3 minutes from the scene, so if they called it given that it must have been clear cut. The Michael Jackson home was about the same distance in the other direction, he was called on scene, then his Doctor demanded that they keep working him all the way in.
I am thinking if it was a cardiac arrest due to Potassium cyanide poisoning, no matter of method to revive him would have worked. The blood wound not be able to carry the oxygen to the muscles of the heart and the brain tissues. It is the same action as carbon monoxide poisoning which kills so many in fires.