Earlier in the season, when Tony was out on the lake with Bobby, he asked what the end would be like. Bobby said something to the effect of probably everything would go black and you probably wouldn't even hear it coming. Tony had a flashback of that conversation before going to bed in the second to last episode of the series. In the end, he didn't hear the shot coming, but he died with his family just as Phil died with his. Then everything went black, just as Bobby predicted.