i think this might be a cultural thing. like as a black person we just be describing people based on their race “who’s that lil lightskin boy she be hangin out with” “what’s that white girl in that one show” <- neutral use of race it’s more like an adjective not indicating any malice
so the surrounding people are one thing but talkin about the killer this might just be a AAVE thing because calling someone a white girl white boy isn’t like malicious it’s just a normal neutral description so if that one sentence is the only reasoning for racial motivations idk id think the motivation was voices in his head