Welcome to HCM
I am sorry about your mother. She shot herself in last month and your father has witnessed it. It was a married life of 34 years. So its natural to have such of grief reaction. Grief reaction like low mood, crying spells, not accepting incident, de realization etc is considered as normal to some extent. But you have mentioned that he replays the incident in his head, he is loosing his mind. This is not normal. Try to talk with him and explore if there is any suicidal intention. Closely watch him and give warm supportive care. It has been about 40 days of your mothers death so such levels of grief are not acceptable. He may develop Post Traumatic Stress
Disorder. I advise you to take him to a Psychiatrist
ASAP for immediate control of his symptoms.
You have mentioned that you are also feeling low to some extent. But if this is not affecting your occupational and social life then its acceptable. Try to help your father, he need help from you.
Dr. Seikhoo Bishnoi