He was the 2nd, but leave it to this dubious administration to continue known erroneous propaganda:
In October 1960, Bolden joined the US Secret Service, becoming their second black agent (after Charles L. Gittens, who was hired in 1956). Bolden was assigned to investigate counterfeiting cases.
https://www.blackpast.org/african-american-history/bolden-abraham-1935/
My apologies, I missed the “on White House Detail” specifics.