Other than the above, there often isn't much to say. Such losses are so painful that there aren't any perfect words or phrases. If there is anything you can do for them, let them know that you can stop by and say, bring a casserole or do some shopping over or invite them over for some coffe and cake to help them stay in touch with life, something concrete. Listening is often far more important, being willing to be with them in this time, particularly if they are good friends. Good luck.