The parents of two Mansfield sixth-graders who told authorities that a school bus driver pulled a knife on them are relieved that the man was arrested Friday. "I don't like the fact it's taken two days before he is arrested, but at least my daughter has witnessed some measure of justice," said Dianna Davis, mother of one of the girls. "At least now, we know the school district's police is taking the matter seriously." Terry Morawski, a Mansfield school district spokesman, identified the driver as William Allen, 66. Allen was arrested about 1 p.m. Friday. He was placed on paid administrative leave after three sixth-graders accused him of threatening them with a knife over cookie crumbs that were reportedly left on a seat. According to reports, two of the three students told their parents that Allen pulled them off the bus Wednesday at Mary Orr Intermediate School and threatened to cut their wrists if they didn't admit to eating Oreo cookies and leaving the crumbs on the seat.