UPDATED 11:45 a.m. | Massachusetts Democratic Gov. Deval Patrick announced Wednesday that his former chief of staff, William “Mo” Cowan, will serve as the state’s interim senator until a new senator is chosen in a June 25 special election.

“Today I have the great honor, privilege and personal pleasure to appoint Mo Cowan as United States Senator in the interim,” Patrick said at a Boston news conference.

Calling Cowan a “highly-respected public citizen,” Patrick tapped the fellow attorney to fill the seat soon to be vacated by John Kerry. Cowan has served in Patrick’s administration since 2009 and is his former chief of staff and chief legal counsel.

When he takes the oath of office, Cowan will become the second African-American senator currently serving, alongside Republican Tim Scott of South Carolina.

In remarks to the press, Cowan mentioned and thanked his mother. “She’s a child of the segregated South; a single mother to my sisters and me after my father died when I was a teenager; a woman who did not have the opportunity to attend college,” he said. “But my mother told me days like today were possible. If you work hard and treat people with respect, there’s very little you cannot achieve in this great nation.”

Cowan said that as he transitions to his new role, he will have “the benefit of Senator Kerry’s outsanding staff,” in both Washington, D.C., and Massachusetts.

Kerry was confirmed as secretary of State and submitted his letter of resignation Tuesday. It will take effect — and the vacancy will become official — at 4 p.m. on Friday.

A special primary will be held April 30. The only currently declared candidate for the seat is Democratic Rep. Edward J. Markey. His Democratic colleague, Rep. Stephen F. Lynch, is expected to announce a bid on Thursday. Former Republican Sen. Scott P. Brown has not yet said whether he will join the special election. But according to an Associated Press report Brown is “leaning strongly” toward running and could announce as early as next week.

See Kerry’s letter of resignation here:

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