Teen says father berated him BUT WHY HE KILLED MOTHER IS A MYSTERY By Tom Lasseter HERALD-LEADER STAFF WRITER COLUMBIA - At the age of 16, Blake Walker shot his parents to death in their home last year, emptying the clip of a 9mm rifle, because he said he could no longer stand his father's constant criticisms about his life, friends and housework. In Adair Circuit Court yesterday, Walker, crying and shaking a little, apologized for the Dec. 8 murders. He loved his father, Walker said, but they never got along. In a statement he wrote for the court, Walker...