. >> secretary leigh ann burke saw mark barton's behavior change over time.king with him in 1984 in texarkana, texas, where he was employed as a chemist for tlc manufacturing, a company that made cleaners and solvents. >> he was always kidding around and laughing and making jokes in the beginning. like i said, he was like a 6-year-old in the body of a 35-year-old man. i mean, he was just a big dennis the menace at first. >> but then a new mark barton began to emerge. >> he would have temper tantrums when he couldn't get formulas to blend right or he would be trying to make a new product and he would try and try and he would have -- he would throw things and, you know, have these little temper tantrums. >> she noticed barton isolated himself and his first wife debra, whom he had met and married while attending the university of south carolina. >> mark always prided himself on the fact that nobody knew what he was. no family ever visited them other than her parents. i didn't even know his parents were alive. i just assumed that his parents had died. >> an only