I'm so sorry for your loss,
I'm sorry if this is long but I've been really struggling with similar .
I lost my brother in January was so unexpected , there was nothing they could do , when they took him off the monitors we were told we could see him, he was still hooked up to all sorts and to see him that way was heartbreaking, was told they will be putting him in a room where it was more comfortable with non of the tubes etc ,I nipped home for a bit as it was my DD birthday so had tea etc. I was hoping he would hang on so I could be there with him, and see him without all the monitors ,tubes etc. My DM phoned to go back up to the hospital to sit and wait ,which of course I wanted , we went back up, the hospital was locked up etc and the staff didn't know why we were there so we had to explain,that we were allowed back in because of the situation, so they unlocked the doors for us, when we got to the room my brother had already passed, he must of just gone as he was still warm and it was only 20 mins after the phone call to go back up , he was still alive when my dm, left. I feel terrible I should of stayed and not gone home , I should have gone up sooner, if they let us back in without a million questions, I might have made it in time. I never really got to say goodbye and see his last breaths, he looked so pieceful alot different to what he looked that afternoon.
Then when we went to the chapel of rest to visit him we didn't know if my other db would be coming up to see him, so I went with my mum and put things in with him, then the next day my mum text to say they had been to see my db again as my other db had decided to come up. I was a little hurt because I would of liked to have gone one last time to see him , and I didn't think my dm was up to going again and I didn't want to mention incase it upset her the more. But I should of asked . When I mentioned I would of like to have gone to see him, she said oh no, it was worse than when we went as it was definalty the last time we would ever see him again.
I should of gone by myself , there was no stopping me so it's not really anyone's fault but I'd would of liked us all to be there one last final time.
I think in grief no one is thinking straight and are just trying to get through each second at a time. I know I sound selfish for having the feelings I do, but nothing can change it now ,it's done.
I haven't any advice on how to deal with any of it, but your not alone.