Philippe Lazzarini: Is UNRWA's mission in Gaza impossible?

Stephen Sackur speaks to Philippe Lazzarini, head of UNRWA, the UN’s refugee agency for Palestinians. This week, six UN relief agency staff were killed in an Israeli strike on a central Gaza school that had been turned into an emergency shelter for thousands. UNRWA’s death count in Gaza since the beginning of the war is over 220. Is his agency’s mission now impossible?