As one Massachusetts regiment was transferred between stations on April 19, a mob of Marylanders sympathizing with the South, or objecting to the use of federal troops against the seceding states, attacked the train cars and blocked the route; some began throwing cobblestones and bricks at the troops, assaulting them with "shouts and stones". Panicked by the situation, several soldiers fired into the mob, whether "accidentally", "in a desultory manner", or "by the command of the officers" is unclear. Chaos ensued as a giant brawl began between fleeing soldiers, the violent mob, and the Baltimore police who tried to suppress the violence. Four soldiers and twelve civilians were killed in the riot.