ALSO: A 26-year-old man arrested Wednesday at the South Burlington Public Library is a “person of interest” in the murders of a former Vermont couple; Vermont and New York state police have arrested the man who authorities say has always been the prime suspect in the 1989 stabbing deaths of his in-laws in their Danby home; The Burlington School District announced Thursday it intends to sue Monsanto over contamination of Burlington High School via hazardous chemicals known as PCBs.