That person is truly gone now.
You may feel many different emotions separately or all at once.
(Sadness, Loss, Guilt, Anger, Loneliness, Grief, Powerlessness)
It may be a cliche, but “you are not alone”.
You can not change what has happened.
You can only “Adjust” how you focus on the future.
Of course, you can do it all by yourself, but that is just a form of self punishment.
Talk to the people around you.
Some advice will be helpful and some will be annoying.
The best “next step” is to join a support group of like minded people.
(People who have experienced similar losses)
The “Rebuilding Seminar” is such a group
You can learn from each other.