A passenger train fell through an open swing bridge into the Richelieu River after the crew failed to obey a stop signal.

[6] By the early 1860s, the cost of building the railroad system together with the failure to achieve expected levels of usage left the company deeply in debt.

[6] On June 29, 1864, a Grand Trunk train carrying between 354 and 475 passengers, many of them German and Polish immigrants, was travelling from Quebec City to Montreal.

A red light 1.6 km (1 mi) ahead of the bridge signalled to the train that the crossing was open and it needed to slow.

[12] One witness described the scene: "It seemed as if they had been placed under a press of enormous power and crushed into an unrecognizable mass of splinters and iron, mixed here and there with car wheels in every position, shreds of clothing, loaves of bread, bundles, and human bodies bruised, battered and covered with blood.

"[10] A journalist from The Montreal Gazette newspaper reported the scene: "A shapeless blue mass of heads and hands and feet protruded among the splinters and framework and gradually resolved itself into a closely packed mass of human beings, all ragged and bloody and dented and dinged from crown to foot with blue bruises.

[10] Roger Cloutier of the Beloeil-Mont-Saint-Hilaire Historical Society stated In 2013: "Several residents of Beloeil and surrounding towns came to lend a hand to rescue as many survivors as possible".

[14] The financially struggling Grand Trunk Railroad company, which feared a blot on its reputation, made a great point of assisting the victims.

[16] Roddick, who had been planning to go to Edinburgh for more medical studies, ended up staying in Montreal as a result of his experiences with treating the injured as Fenwick was impressed with his skills.

[17] The Grand Trunk Railway tried to blame the disaster on the conductor and engineer for failing to obey the standing order to stop before crossing the bridge.