Unseen footage sheds light on "Hat Man" in Kassanndra Cantrell case

"48 Hours" has obtained never-before-seen footage of the mysterious killer known as the "Hat Man" in the murder case of Kassanndra Cantrell. The investigation relied heavily on digital forensics, including cellphone records, deleted texts, vehicle location data, store receipts, surveillance videos, and even an underwater dragnet to find the remains of Cantrell and build a strong homicide case against her ex-boyfriend Colin Dudley. Dudley pleaded guilty to first-degree murder and was sentenced to 26 years in prison.