Dunn is married to Maria-Elena Dubourt and has two sons, Tom and Brian.

Since 1988, he has been engaged with Africa, serving in Burundi, Mauritius, Tanzania, Zambia, South Africa, and Togo, and as deputy director and director of the State Department's Office of East African Affairs.

From 2002 to 2005 he served as Principal Officer at the Consulate General in Johannesburg, South Africa.

[3] Following Togo, Dunn was assigned as a faculty member at the National War College, where he also served as Deputy Commandant.

Shortly after his retirement at the end of 2010, Dunn was directed by President Barack Obama to return to service to perform the duties of the Alternate Representative for Special Political Affairs at the United States Mission to the United Nations in New York, a position he held for seven months.