Officer Justin Barrett, who is white, sent an anonymous mass e-mail calling Gates a "jungle monkey" to fellow National Guard members after the professor's July 16 arrest in Cambridge, Mass., The Boston Globe reported on its Web site Wednesday.
When confronted by a supervisor, Barrett, a two-year veteran, admitted he had sent it, the Boston Herald reported.
Boston Police Commissioner Edward Davis learned of the e-mail Tuesday and stripped Barrett of his gun and badge, WCVB, Boston, reported Wednesday. It remained unclear when Barrett allegedly sent the e-mail.
Davis told Mayor Thomas M. Menino of the e-mail Tuesday night, and the mayor compared Barrett to a cancer, saying he is "gone -- g-o-n-e'' from the force, the Globe reported.
"That stuff doesn't belong in our city and we're not going to tolerate it," the Globe quoted Menino's telling Davis.
Barrett faces a termination hearing in the next week, police spokeswoman Elaine Driscoll told the Globe. He has no previous disciplinary record, she said.
The Globe said Barrett could not immediately be reached for comment.
The arrest of Gates sparked a national debate on relations between police and minorities. Sgt. James Crowley, who is white, arrested Gates, on a disorderly conduct charge, which was dropped. Gates and a taxi driver had been trying to force open a jammed door at the professor's house.