( CNN ) -- The director of the Peace Corps , Aaron S. Williams , announced Tuesday that he is stepping aside after three years on the job . `` This has been a difficult choice because serving in this position has been the highlight of my public service career , '' he said in his message to colleagues . `` It has brought my personal journey in government full circle - from Peace Corps Volunteer to Director . It is time , however , for me to shift my focus to my family . '' Williams , who leaves effective September 17 , served as a volunteer in the Dominican Republic from 1967 till 1970 . He was sworn in to the organization 's top job in August 2009 and immediately found himself dealing with security issues related to the volunteers . Four months earlier , 24-year-old volunteer Kate Puzey had been killed in Benin . And last year , an ABC News investigation reported that more than 1,000 young Peace Corps volunteers had been sexually assaulted during the prior decade . Peace Corps volunteer guilty of abusing children . Also last year , a Connecticut man pleaded guilty to traveling to South Africa to engage in illicit sexual conduct with children while he was a Peace Corps volunteer there . At the time , Williams said , `` The Peace Corps has no tolerance for abuse of any kind , and our deepest sympathies are with all the victims involved . '' He vowed that the Corps would ensure that the victims were properly cared for and treated . In congressional testimony in March 2011 , he said , `` While the Peace Corps can not eliminate every risk volunteers face during their service , I am committed to making sure that we do everything we can to protect volunteers and provide effective support to them and their families when a tragedy occurs . '' Williams has worked with Congress to codify reforms and increase support to volunteers in the field , including hiring a victim advocate ; enhancing safety and security , as well as support and response for volunteers ; and improving training for volunteers and staff , the organization said . In a statement on Tuesday , President Barack Obama credited Williams with having helped `` in reforming and modernizing the agency . '' Deputy Director Carrie Hessler-Radelet will serve as acting director upon his departure . In all , more than 9,000 volunteers serve in 75 host countries , according to the Peace Corps . Since its establishment in 1961 , more than 200,000 Americans have served . Ghanaian police : Peace Corps volunteer kills suspected robber .
`` It is time ... to shift my focus to my family , '' Williams says . He leaves office September 17 . His 3-year tenure was marked by efforts to ensure the safety of volunteers abroad .