The opportunity came on 13 March 1940, almost 21 years after the Jallianwala Bagh killings: A joint meeting of the East India Association and the Central Asian Society (now Royal Society for Asian Affairs) was scheduled at Caxton Hall, and among the speakers was Michael O'Dwyer. Singh concealed his revolver in a book specially cut for the purpose and managed to enter the hall. He took up his position against the wall. At the end of the meeting, the gathering stood up, and O'Dwyer moved towards the platform to talk to Zetland. Singh pulled his revolver and fired.
O'Dwyer was hit twice and died immediately. Then Singh fired at Zetland, the Secretary of State for India, injuring him but not seriously. Incidentally, Luis Dane was hit by one shot, which broke his radius bone and dropped him to the ground with serious injuries. A bullet also hit Lord Lamington, whose right hand was shattered. Singh did not intend to escape. He was arrested on the spot.
His weapon, a knife, his diary, along with a bullet fired on the day are now kept in the Black Museum of Scotland Yard.