Happy Ending?

In the movie Mystic River there are some unexpected twists and turns. In the beginning you never really know what happenes to Dave but all you know that is when he comes back he's not the same person. The death of Jimmy's daughter is what brings them all back together. Probably not how any of them pictured it. The same night his daughter was killed, Dave thought he killed someone. Coincidence ? The guilt Dave and his wife had from that gave them away to police, who was also their childhood friend Sean. Even though he didn't do it he felt the guilt and that began to settle in on his wife. The role guilt plays in this movie is huge. Dave is already disturbed from his childhood, Jimmy made a few wrong moves, like killing Dave for something he didn't do and Sean was this guy who was strictly business. So when he had to deal with the case of his friends dead daughter that's all it could be. With all the allegations and things dealing with this case all the guys who started off as friends learned something about themselves. When Jimmy killed Dave at the end for admitting something he didn't do one can only think that was his way out or that he no longer wanted to live. Jimmy gets away with it as far as we know. So, is it a happy ending because Jimmy was at peace besides killing his childhood friend and Sean had his wife back? Or is it not. The choice is yours.