he went too far. >> reporter: police also used a under surveillance tape from that home depot to figure out the person who dropped off the btk letter was driving a car registered to dennis rader's son. but to make certain they had their man, they needed a dna match. so authorities got a warrant for a tissue sample from rader's daughter on time at a kansas medical clinic. tests showed it was a close match to the evidence drawn from the crime scenes. it was now early in the week of february 21st, 2005, and former police chief remembers quite well when he got the news he had waited more than 30 years to hear. >> it simply said, we got him. he said, it's just a matters of time. we got him. >> locked up, choked up. >> that sunday was the lowest day of my life is there tears from a killer, not for his victims. when "confessions of btk" continues.