On September 15, 2014, the family of Ebola virus disease patient Marthalene Williams were unable to summon an ambulance to transfer Williams to the hospital. Their tenant, Duncan, helped to transfer Williams by taxi to an Ebola treatment ward in Monrovia, Liberia. Duncan rode in the taxi to the treatment ward with Williams, her father, and her brother. The family was turned away due to lack of space and Duncan helped carry Williams from the taxi back into her home, where she died shortly afterwards.[11]

On September 19, Duncan went to the airport in Monrovia, where according to Liberian officials Duncan lied about his history of contact with the disease on an airport questionnaire before boarding a Brussels Airlines flight to Brussels. In Brussels, Duncan boarded United Airlines Flight 951 to Washington Dulles Airport.[12] From Washington, he boarded United Airlines Flight 822 to Dallas/Fort Worth. He arrived in Dallas at 7:01 p.m. CDT[13] on September 20, 2014,[1][14] and stayed with his partner and her five children, who live in the Fair Oaks neighborhood of Dallas.