"Dateline’s” Edie Magnus reports on the first exclusive look inside the mind of the man behind the initials "BTK." An exclusive interview obtained by “Dateline” was conducted by Harvard neuropsychologist, Robert Mendoza, who was hired by Rader’s defense team to assess his sanity.

During the two-hour “Dateline,” Magnus chronicles Rader’s killings, his subsequent obsession with the media, his arrest — which he refers to as “Black Friday” because he claims he didn’t see it coming — and ultimately, his willing confession. Also included in the broadcast are never heard before details about how and why he chose his victims.

Dennis Lynn Rader (born March 9, 1945), also known as BTK (an abbreviation he gave himself, for "bind, torture, kill"), is an American serial killer who murdered at least ten people in Wichita and Park City, Kansas, between 1974 and 1991. Although Rader occasionally killed or attempted to kill men and children, he typically targeted women. His victims were often bound, sometimes with objects from their homes, and either suffocated with a plastic bag or manually strangled with a ligature.

In addition, Rader stole keepsakes from his female victims, including underwear, licenses, and personal items. He often sent taunting letters to police and media outlets describing the details of his crimes. After a thirteen-year hiatus, Rader resumed sending letters in 2004, leading to his 2005 arrest and subsequent guilty plea. He is currently serving ten consecutive life sentences at the El Dorado Correctional Facility.

*FIXED COPY* VIDEO AND AUDIO ARE NOW SYNCED. TV ADVERTISEMENTS ARE REMOVED IN THIS UPLOAD.

BTK Killer Documentary

Dennis Rader Documentary

Serial Killer Documentary

MSNBC