Ahmed Assem has become the poster child of what Muslim Brotherhood leader's are calling a massacre — last Monday's assault by security forces on angry Islamist protesters. Assem was a photographer who filmed his own death. An army sniper shot him down. The killing has torn Assem's family apart. His brother is a police officer who blames the Brotherhood for the violence, but the family, like Egypt itself, is now deeply divided and unsure what is to come.