I'm sorry scockery, man that's tough.
He may have had an aneurism though too... My cat some years ago collapsed and twitched making a gagging type sound and his eyes rolled back. My brother tried clearing his throat as we thought he choked, and then my brother who was an EMT at the time did a type of CPR on him but he was gone. We took him to the emergency pet hospital and they let us knwo he'd died of an aneurism and it was pretty much instantaneous.
Cats usually have a reflex to get hairballs up and don't choke on them, as I understand it.
Losing a pet sucks, and I really feel for you. I was tearing up the other day about my cat I lost just recently. I'm making a mold for a headstone for where I buried him and it was hard just to make the mold box without starting to lose it.