That reward is great, but it needs to be presented to target audiences in a tangible way, not just as a relatively vague theory.
Could the reward be posted electronically with links to a bank account where interested parties can verify the amount? Maybe include a letter from a bank official confirming that the account is real and a letter from a judge stating that payment is mandatory by law.
In regards to target audiences, the motive for the crime can probably be divided into two broad categories:
A. Haters
B. Personal
Inside information could well depend on somebody close to unsavory types acting on the reward offer.
White supremacists are probably the statisticaly more likely population for the "Hater" motive. Could it be arranged for tangible reward information to appear as "pop ups" on dark web or "barely tolerated" social media venues?
Are there area businesses that that have a far right customer base? I once knew of a gun range that sold guns and right wing literature. Maybe a night club, motorcycle shop, bar etc? If so, tangible reward posters are put up around the business in question. Any known white supremacists have tangible reward information put up in their neighborhoods.
Likewise, one does not need to be white to hate and having a similar melanin content as the victims does not guarantee warm and fuzzy feelings.
Has any local group of black American high school students ever developed a dislike of African immigrant students? What about a street gang or wanna'be gang? If so, they get the same targeted tangible reward treatment as their white counter parts, but with perhaps a different priority. Ditto for Hispanics.
The "personal" motive (and perhaps more likely motive).....
Could tangible reward information be posted at mosques and churches with an African member base? African grocery stores, restaurants, and places of employment with large numbers of African employees should also be approached for permission to post tangible reward information.