SANFORD, N.C. (AP) — Lowe's store manager Michael Hollowell had heard the tornado warnings but his first clue that the danger was outside his front door came when he saw his staff running toward the back of the home improvement store. More than 100 employees and customers screamed in near unison when the steel roof curled off overhead Saturday. The store was becoming part of the wreckage left by a ferocious storm system bristling with killer twisters that ripped through the South.