Hundreds of protesters demanding an investigation of Mayor Rahm Emanuel's administration flooded downtown Chicago streets Wednesday afternoon as part of a citywide walkout just hours after Emanuel publicly apologized for the shooting death of Laquan McDonald and vowed to fix broken Chicago police practices.The group chanted "Whose city? Our city," "Who's got to go? Rahm's got to go," and "No more killer cops."Demonstrators gathered at Daley Plaza at noon and started marching on North Dearborn. Police briefly detained two people during the protest near Dearborn and Washington as several other activists gathered around the vehicle chanting "Hell no, we won't...