I am so sorry for your pain and your loss. What a tragedy.
Nothing we say will bring him back. You can take comfort in that you were there supporting him.
I hope time helps.
I know those last moments must have been terrible. For your sanity, try put them out of your mind. When those images return, put them out of your mind and replace them with happy times.
You can document what happened. Note the names and the times, and the powers-that-be will be able to determine who was there, who was consulted.
If you feel there should be something done about it, your best bet, I think, is to report the nurse, or whomever told you the information, to their corresponding college. You can Google: 'reporting a doctor for misconduct' in your province or territory, and you will find what you need to do.
It took me months to get to this point, but after dad died I reported his doctor to the College of Physicians. I was happy that when the College calls the doctor they jump. High. They worked with the nurses, as well, to improve circumstances in the nurses office, too. I know I improved the situation for those who would follow, and his other patients in the long-term care.
I hope you find some comfort. Let us know how you are doing.