Two days after all of his bosses on the Fairfax County Board of Supervisors were returned to office by voters, Fairfax County Executive Anthony H. Griffin announced Thursday that he will step down in April 2012 after more than a decade of service in Virginia’s largest jurisdiction.

Griffin, who had alerted Board members earlier this year of his interest in retiring in 2012, has served as one of the most powerful, behind- the-scenes leaders in the region since having taken charge of the county’s day-to-day workings in 2000. His tenure is the longest on record since the post was created in 1952.

“I enter the next phase of my life with mixed emotions,” Griffin said in a statement to the county’s approximately 11,000 employees. “I am excited but uncertain about my future, and I will miss continuing in my current capacity.”