CHICAGO (AFP) - An escaped convict allegedly murdered an elderly woman as part of a bizarre plot aimed at assassinating US President Barack Obama after a cross-country killing spree, court records showed. Maybelle Schein, 75, was discovered with her throat cut in the bedroom of her South Dakota home on Saturday afternoon. Police used the OnStar tracking device in her Buick to find the car driving on a highway hundreds of miles away near Madison, Wisconsin. James Vernon McVay, 41, told police of the plot after he was arrested in the woman's car after a brief chase and standoff.