 Ken Bruno hasn't been back here on this street in Boston's South End since 2016, but he remembers what took place that October day as though it were yesterday. Bruno is a carpenter who was working inside a townhouse in this upscale neighborhood when he stepped outside for a quick cigarette. While he was standing near the edge of a trench where two men were working, the unimaginable happened. I'm looking down, and the guys are down there walking.