One of Pittsburgh’s most solemn days began with hundreds coming together in anguish and grief in synagogues and at gravesides, to start the services for those killed as they prayed on the Sabbath. In the afternoon, they came together again, in shivas to honor the dead and comfort the living, and, later by the thousands, in solemn marches of protest around the Squirrel Hill neighborhood where the attack took place on Saturday.