Walker worked for Al Jazeera English in the United States from 2008 to 2016. First based at Al Jazeera English's main US bureau in Washington, D.C. and then in Al Jazeera America's San FranciscoFault Lines show hub, he was a presenter on Fault Lines, the channel's flagship news magazine about the Americas, and reported from across the continent.[1]
Before joining Fault Lines, Walker was a foreign correspondent with a particular interest in Haiti. Al Jazeera English was the only international TV news network to maintain a bureau in Haiti after the 2010 earthquake[2] and Sebastian arrived in Port-au-Prince less than 24 hours after the earthquake hit to report on the damage. He then stayed on for a year and a half to document the progress of the relief effort.[3] Walker was instrumental in discovering and documenting the United Nations' role in the 2010–13 Haiti cholera outbreak, the largest such outbreak in recent history.[4] Walker won a DuPont-Columbia University Award in Broadcast Journalism for his work in Haiti.[5] He continued covering Haiti at Fault Lines, which was awarded a News & Documentary Emmy Award for "Outstanding Investigative Journalism in a News Magazine" on 30 September 2014 for the episode "Haiti In A Time Of Cholera",[6] which also earned a Peabody Award.[7]
Prior to being based in the Americas, Walker worked in the Middle East. He served at the channel's main broadcast centre in Doha, Qatar, where he helped to launch the channel.[citation needed]