The Church Killer went nuts about blacks after a girl he liked went for a black man instead of him,

http://www.addictinginfo.org/2015/06/22/dylann-roofs-cousin-says-killer-went-over-the-edge-after-love-interest-chose-black-man-over-him/

The girl chose the black suitor 2 years ago and Roof got into the racist craziness after that