The FBI says Little, whom the bureau said "may be among the most prolific serial killers in U.S. history," has a criminal record dating to 1956. But only recently has he opened up about the long list of killings he has said he committed. Agents who have interviewed Little say he remembers his victims and the killings in great detail, including where he was and what car he was driving. But he could provide little help on dates, creating a challenge that the FBI hopes Little's drawings can help surmount.