What are the correct procedures when someone accidentally touches high voltage live cable and is getting electrocuted?
The health and safety answer is to shut off the power and then deal with the medical issues.
There is another answer but it depends critically on the knowledge and judgement of the person carrying out the action. This is to remove the victim from the power using an insulating material. In this case as it is a lighting circuit the highest voltage likely to be there is 240V. So a piece of construction timber or a pair of insulating gloves should be sufficient. The knowledge and judgement plays into knowing what you are dealing with in terms of risk (how big is the voltage) and how to mitigate it (properties of insulators) so this can not be recommended as a course of action for all and sundry.