Fear and helplessness are often the source of anger. Ask yourself, what might they be afraid of? Are they really angry at you, the person trying to save their loved one? That would be so counterproductive. Are they, rather, lashing out in fear?
Step back emotionally, let go of defensiveness, it’s not really about you. A compassionate response might defuse the situation, “I can’t imagine what you are feeling, but I am here, we are all here, with you.”
And then take a Moment for self-care. And schedule another for later on.