Usually if anger is being spoken about around the construct of grief, it likely has to do with Elisabeth Kubler-Ross' model of grief. In the model, she describes five stages. The first is denial, second is anger, third is bargaining, fourth depression, and then the fifth and final is acceptance. In her model, she proposes that if people are struggling with grief, they're going to move through these various stages. First, sort of, denying and not really believing or fully accepting that it's happening, then becoming incredibly angry, possibly at the world, God, themselves, if some of their behavior was part of the reason for the disease or something like that. Then some kind of bargaining, where there's almost a negotiation as if they change their lifestyle, if God will make it not be the case. And then some depression where they might, in fact be very down, until moving towards acceptance.
Now there have been a number of scientific studies that haven't necessarily supported this model fully, although there's been some recent research that might contradict that it's unclear. What I can say is that having worked with clients that are going through loss or coping after the death of a loved one, I still find paying attention to these five stages, not necessarily that everyone will move through all of them, and not necessarily that they'll move through in any particular order, but paying attention and helping clients being able to sort of accept and acknowledge where they are regardless. If they're struggling with anger or the depression or any of those things, it can be a helpful for clinicians guide clients through this difficult process of grief.