Task: Question Generation
Input (English): He was killed on 2 March 2009, possibly by soldiers in retaliation for the assassination of General Batista Tagme Na Waie, the head of the joint chiefs of staff, killed in an explosion. Vieira's death did not trigger widespread violence, but there were signs of turmoil in the country, according to the advocacy group Swisspeace. Malam Bacai Sanhá was elected after a transition. In the 2009 election to replace the assassinated Vieira, Sanhá was the presidential candidate of the PAIGC while Kumba Ialá was the presidential candidate of the PRS.
Output (English): When was Vieira killed?