According to Song dynasty records, during the Hanshi and Qingming Festivals, the capital city would be filled with willow branches on every house, even in deep alleys.
Emergency services say children are among the casualties of the attack which took place on the Christian festival of Palm Sunday, what Ukrainians call Willow Sunday.
The most popular ones, such as tomb upkeep and repair, spring outings, kite flying, and putting willow branches on gates, have been an important part of this festival since its beginning.