1) He is clearly hiring based on a fetish he has.
2) They were hired to replace male, white, african-american, or hispanic members of his department over a period of ~2 years. The area is almost entirely a white and/or hispanic population so there is no way this is coincidence.
3) The odds of a guy rolling the same 20 sided die 12 times and always coming up with the same number is highly improbable. Roughly 5% of the applicants were female and Asian. I somehow doubt the most competent were always in that 5%.
4) Its a baker's dozen (13).