Boston Mayor Marty Walsh, right, chats with Nicole Boggio, of Severna Park, MD, left, at a sidewalk cafe on Boylston Street near the finish line of the Boston Marathon, Monday, April 14, 2014, in Boston. A year after twin pressure cooker bombs shattered the marathon and paralyzed the area for days, federal prosecutors say they have a trove of evidence ready to use against the surviving suspect, but many questions remain. (AP Photo/Steven Senne)