US vice-president cancels planned visit to Independence Square as relatives of revolution dead vent angerThe Ukrainian president has been heckled by relatives of 100 protesters killed in Kiev’s Euromaidan revolution at a memorial ceremony for the victims.The relatives, frustrated by Petro Poroshenko’s failure to bring officials of the previous government to justice, shouted: “Who is a hero for you, Poroshenko?”, “Where are their killers?” and “Down with Poroshenko!” They also attacked him for failing to keep a promise to confer the title of national hero on the victims, which would bring financial benefits to their families.