 Complete the following phrase:  People were assembled in Jallianwala Bagh, Amritsar to celebrate the important Hindu and Sikh festival of Baisakhi, and to peacefully protest the arrests. Udham Singh and his friends from the orphanage were serving water to the crowd. Troops under the command of Colonel Reginald Dyer opened fire on the crowd, killing several hundred; this became known variously as the Amritsar Massacre or the 