Identifying the Stage of Grief

A nurse is providing care for a patient who has just experienced the loss of a long-term partner. The patient expresses feelings of anger and guilt, stating, 'I should have been able to save him; I should have done more.' In the context of grief and loss, the nurse recognizes that these feelings may indicate which of the following stages of grief as proposed by Kübler-Ross?

Which stage of grief is the patient most likely experiencing?