Similar thing happened to my old man.
He was fine one minute then got a bit groggy, 1h later at 1am in the morning i had had enough and called an ambulance, 2h later he had gone.
I never said the things i wanted to say some of my last words were arguing with him that we need to go to hospital now, he was very stubborn about it.
Help your mum, mine was the same as yours. She dosn't drive and had no confidence, my dad did nealry everything for her.
good luck mate, one thing i found just cry when u need to really just get it out.