WHIT. >> MARYALICE, THANK YOU. >>> NOW TO SOME NEW AND DISTURBING REVELATIONS IN THE BRIAN LAUNDRIE/GABBY PETITO PACE. SEVERAL PAGES FROM LAUNDRIE'S NOTEBOOK FOUND NEAR HIS BODY IN FLORIDA HAVE BEEN MADE PUBLIC BY HIS FAMILY AS ATTORNEY. >> Reporter: IT WAS A CASE THAT GRIPPED THE NATION, AND TONIGHT FOR THE FIRST TIME, WE'RE HEARING FROM BRIAN LAUNDRIE IN HIS OWN WORDS, AFTER INVESTIGATORS SAY HE MURDERED HIS GIRLFRIEND GABBY PETITO DURING A CROSS-COUNTRY ROAD TRIP LAST SUMMER. THE FBI SAYS BRIAN ADMITTED TO KILLING GABBY IN THIS EIGHT-PAGE HANDWRITTEN LETTER RELEASED BY THE LAUNDRIE FAMILY ATTORNEY. BUT BRIAN CLAIMING IT WAS A MERCY KILLING, THAT GABBY HAD FALLEN AND WAS IN PAIN. WRITING IN PART, "I ENDED HER LIFE. I THOUGHT IT WAS MERCIFUL, THAT IT IS WHAT SHE WANTED, BUT I SEE NOW ALL THE MISTAKES I MADE. I PANICKED. I WAS IN SHOCK." FEDERAL AUTHORITIES SAY BRIAN STRANGLED GABBY TO DEATH IN WYOMING AND RETURNED HOME TO FLORIDA ALONE, SPARKING A NATIONWIDE SEARCH. HER REMAINS LATER FOUND NEAR GRAND TETON NATIONAL PARK. BRIAN AND HIS FAMILY DECLINED TO SPEAK WITH LAW ENFORCEMENT OR GABBY'S PARENTS. BRIAN THEN DISAPPEARED HIMSELF. AUTHORITIES SAY THEY FOUND HIS BODY IN A SWAMP NEAR HIS FAMILY'S HOME NEXT TO A NOTEBOOK WITH THAT WRITTEN CONFESSION, SAYING HE DIED FROM A SELF-INFLICTED GUNSHOT WOUND. GABBY'S FAMILY HAS FILED A CIVIL LAWSUIT AGAINST BRIAN'S PARENTS, ACCUSING THEM OF INTENTIONAL INFLICTION OF EMOTIONAL DISTRESS. THE LAUNDRIES' ATTORNEY HAS CALLED THE CASE BASELESS AND IS SEEKING TO DISMISS IT. A JUDGE WILL DEC