I would say I understand how you feel due to events from my past, but the fact is, I DON'T know how you feel. No one besides you can really know what you are feeling right now. Its unfathomable to someone not actively experiencing it, and even then it evades any attempts of definition.
I hope you can have a good recovery from the grief you are experiencing, and live on without dwelling on it for your mothers sake, and don't let this tragedy grow into a chain of events.
Always remember that any feelings you have are perfectly fine, no matter what. During grief everyone acts differently and has odd emotions. Be sure to share what you feel with the people you trust when you are ready to talk to others.
Lastly, I hope you have found enough time to think in silence about what has happened, as that can be the one thing you want most ironically taken away by those with purely good intentions.
Best Wishes, and may your mother rest in peace.