I lost my mother in a very sudden incident, and I can’t stop reliving the situation on how she could have been saved. I can’t stop feeling that it was preventable and my fault.
Many people feel this even when it was not preventable. Reliving the experience is a way to try to work it through and gain control of the situation. Feeling helpless is one of the worse feelings we can have. We try to find a way we could have helped, believing if we could have done something, things would have been different. This is an attempt to relieve our helplessness and bring the person back. Reassure yourself that it was not your fault trying out scenarios that confirm this.
Talk to someone who can respond to you in realistic terms. It is hard not to feel guilty, but the reality is that most deaths we can do nothing about.