As Anne said, I think it's pretty typical of people to want to fix things so that people they love don't hurt anymore. He wants to be helpful. Is there a way he could be helpful that isn't leaving you alone, such as holding you while you cry as a way for him to be with you? Would you be able to tell him that doing X does ease your pain and help you process your grief? And through processing your grief, he is helping it be "fixed".

While being able to sit with the feeling of helplessness is his work to do, you can help him by showing him that he's not completely helpless in this situation and teaching him what you need to feel comforted when you need or could use his support.