JUDGE. JURY. EXECUTIONER. On a cold January morning, the killer executed Assistant District Attorney Mark Hasse in broad daylight. Eight shots fired a block from the Kaufman County Courthouse. Two months later, a massacre. The day before Easter, the couple slept. Bunnies, eggs, a flower centerpiece gracing the table. Death rang their doorbell and filled the air with the rat-a-tat-tat of an assault weapon discharging round...