Freeway Phantom
The Freeway Phantom was a serial killer who was active in Washington, D.C. from April 1971 through September 1972. Over this period, he abducted six African-American girls, ranging from ages 10 to 18, sexually assaulted them and killed them - usually via strangulation but also via stabbing a few times - discarding their bodies along the sides of various major highways.
A proper motive has never been discerned about the Freeway Phantom's killings, though it should be noted that all of his victims were underage (except one) African-American girls, so it could be theorized that he was a pedophile as well as racist towards African-Americans. Though this is mererly a theory and has no basis in fact.
The only clue that the authorities ever got from the killer was a note found in the coat pocket of Brenda Woodward, the Phantom's fifth victim.
It read:
This is tantamount to my insensititivity to people especially women. I will admit the others when you catch me if you can! Free-way Phantom
Following the murder of his sixth victim, Diane Williams, on September 5, 1972, no more murders attributed to the Freeway Phantom ever took place again. To date, the Freeway Phantom has never been apprehended and his identity remains a mystery.