On April 19, 1861, Union troops moving through Baltimore were attacked by angry mobs of Southern sympathizers. It left 14 people dead and lasted for three days. Many rushed to the outskirts of Baltimore to set up roadblocks to try to prevent Union troops from passing through the city. The riots and protests might have led to secession had they been organized. But Union troops moving to Washington, D.C. were quickly changed to being transported by water to avoid the tense situation in Baltimore. Throughout the winter and spring of 1861, Maryland decided against neutrality and against joining the Confederacy. But in May of 1861, acting without orders, General Benjamin Franklin Butler marched into Baltimore. He occupied Federal Hill and set up cannons threatening anyone who would move against them. Lincoln was furious and promptly relieved Butler of his command. Still, the Massachusetts troops were left on Federal Hill. To prevent further trouble Lincoln suspended "habeas corpus" and imprisoned without charges or trials one sitting U.S. congressman as well the mayor, police chief, entire Board of Police, and the city council of Baltimore. 