I think the most heartfelt thing to say is that you are so very sorry that this has happened and/or this must be so hard for you. "If you like, I can bring you some comfort food, pick up your children at school, babysit, elderly sit, etc."The bottom line is to show empathy and compassion, and above all acknowledge the person's feelings and pain. If possible, offer specific help if appropriate. Advice, especially telling someone how to feel, is a no-no, e.g.,"Try to be more positive or if you believe in miracles they'll happen, or there's an article I read that proves there's a cure, or suffering makes you stronger," etc., etc. Just be there and if you don't know what to say, a hug among the vaccinated, now that Covid restrictions are eased, can suffice.