Saying goodbye to a loved one is never easy; whether it is an expected passing or sudden and unexpected.  Let the grief process flow.  You will have good days and bad. There will be times and days that are harder than others.
Know that your loved one is at peace now. Their struggle is over.  They will still be with you in your heart and in your memories.  You have their love and caring in you.  Be gentle towards yourself this traumatic event will take time to adjust too.