The homicides of two Bellingham sex offenders in August did not provoke much sympathy. But they did prompt alarm from police and corrections officials, because Hank Eisses and Victor Vazquez apparently were killed by a vigilante. Within weeks, a felon named Michael A. Mullen, 35, turned himself in and confessed to, indeed, being a vigilante. "I am sorry that I felt the need to kill two people in order to have my message heard," he wrote to The Seattle Times from jail in September. "Yet on the flip side of that coin, if my actions saves just one child, then...