This weekend, Tucson joined Virginia Tech, Fort Hood and the Holocaust Museum as locations of mass killings that have rocked the nation. Were there warning signs that disturbed people might commit mayhem? During five disruptions in classrooms and libraries, Jared Loughner frightened teachers and classmates at Pima Community College. Police were used to deliver a letter telling him he couldn't come back unless he got "mental health clearance" indicating he was not "a danger to himself or others." In the aftermath of Saturday's shooting, were there signs that should have provoked action? Did the college drop the ball? Do laws about mental illness and privacy require that we wait too long, or are they needed to protect sick people from misunderstanding and over-reaction?