black male, blackmail

Black male or black male ( two words ) most commonly, means an American man or boy of African heritage--
We think a black male teacher would have a positive effect.
A young black male is missing; there's a poster in the store window.

Blackmail or blackmail ( one word, rhymes with black male ) is a slang or old-fashioned word for "extortion", meaning threatening to reveal a secret, and demanding payment or some other consideration to keep quiet--
He is trying to blackmail his boss; he found something irregular in the accounts.
She's wants a dirty secret on each member of the jury, something she can use to blackmail them.

Now that you know that, you can say--
"An unidentified black male was injured in the accident, and the driver is trying to blackmail the witnesses."