He first traveled to the Congo in 2001 to work for a local human rights organization, Héritiers de la Justice, in Bukavu.
Stearns attended Swiss public school in Arlesheim and Muenchenstein, on the outskirts of Basel, and spent a year in Laja, Chile, on an exchange program.
Between 2005 and 2007, Stearns was based in Nairobi, Kenya, as a senior analyst for the International Crisis Group, working on the Democratic Republic of the Congo, Rwanda and Burundi.
In 2007, he left to spend a year and a half researching and writing Dancing in the Glory of Monsters, a history of the Congo wars of 1996–2003, based on interviews with leading protagonists of the conflict.
According to eyewitness testimony, phone records and other documentary evidence, the Rwandan government had provided military support to the National Congress for the Defense of the People (CNDP) rebel group, while the Congolese government had collaborated with the Democratic Forces for the Liberation of Rwanda (FDLR) rebels, as well as other Congolese armed groups.