In 1638 the Maryland Assembly considered a bill by which it would have directed that the sheriff choose one of his servants to execute “all corporall corection shame or other punishment to be inflicted on the Body” of the condemned and that if he had no servant the governor and his council would appoint a hangman. The bill did not pass but reflected the aversion the ruling class had in the execution of their laws. The hangman's duties would consist of public whippings, dunking and locking in stocks [all shames] for servants guilty of insubordination. Beatings were regulated to 40 then 30 lashes for whites. However, a black could be beaten as often, and with as many strokes, as his master saw fit.
Beginning in the 1680s Maryland hangmen would be selected as follows:
Had all been sentenced to hang, and had these sentences commuted in return for their service as a hangman.
-Pope Alvey was directed to hang another felon to earn a reprieve until his sentence could be overturned, and it was
-John Collins, was a servant who was sold into servitude again when he failed to pay his fees after being convicted of two thefts. He seems to have been the hangman while he was a serving his second term.
-Thomas Poney was a convict servant who was advertised as a hangman when he ran away.
-Negro Tony  was one of five defendants charged in the murder of their master. When he was acquitted he was made to serve as their hangman.
There were certainly many more.
One comparison of interest is that over 4,000 white servants ran off during a period that only saw 63 of them executed, suggesting that some died at their master's hand in private corrections sessions. There would be successful cruelty charges brought by servants against masters in the colonial and early American period, including bizarre mutilations, for which the masters were merely fined or censored.
Escaped slave listings in Virginia and points south would describe blacks as slaves. But in Maryland the custom was as so, Negro Jack, Negro Ned, etc.