I disagree, if you violate the basic principles of medicine you are not a physician. Being a doctor is more than just having a medical degree, you must act in an ethical manner, ie. not murdering people in the capacity of a state hitman.
They are acting in an ethical manner they just have different obligations to what you deem acceptable. In this case they are weighing beneficence for the greater society and advocacy for the state vs maleficence against the convict.
Isn't it obvious?
Yes, it is obvious they are using agents that will tick all the boxes for a death. Again you are ignoring why they can't use anaesthetics.