LAMB By Jeff Amy and Kevin McGill Associated Press GAUTIER – A university instructor told police he killed his girlfriend at the home they shared in Mississippi, where investigators found a note that said “I am so sorry” and gave no hints that he was already headed a few hundred miles north to kill a colleague, police said Tuesday. Shannon Lamb called 911 on Monday, telling a dispatcher he had killed 41-year-old Amy Prentiss at the home they shared in Gautier.