MIDLAND CITY, Ala. — A standoff in rural Alabama went into a second full day as police surrounded an underground bunker where authorities said a retired truck driver was holding a 5-year-old hostage he grabbed off a school bus after shooting the driver dead. A normally quiet dirt road was teeming with activity Thursday around the siege that began late Tuesday. More than a dozen police cars and trucks, a fire truck, a helicopter, officers from multiple agencies, media and at least one ambulance crowded the stretch where the dead-end residential road branches off a U.S. highway near Midland City, …