Riding in the back of those large green safari vehicles with tourists, day in day out, something unsettled Umwiza.
Washington once labelled Khartoum a hub of the "axis of evil".
President Muhammadu Buhari has not yet directly commented on the shooting, drawing fierce criticism for his silence.
White House says Sudan's transitional government has deposited $335 million for compensating survivors and family members.
Michael Nyang had visited a KCB bank branch before developing complications.