"Canadian insurgents led by William L. Mackenzie of Ontario had been waging revolution against British rule. Thwarted in an attempt to capture Toronto, the rebels fell back to Navy Island on the Niagara River, where they established a government-in-exile committed to an independent Canada. Americans sympathetic to the revolution transported supplies to the island on the steamship Caroline. In December 1837 Canadian militia, on orders from Britain, seized the Caroline in U.S. waters, set it afire, and sent it hurtling over Niagara Falls in flames. One American was killed and several injured. In a message to Congress, President Van Buren denounced the incident as "an outrage of a most aggravated character... producing the strongest feelings of resentment on the part of our citizens in the neighborhood and on the whole border line." Although he ordered American forces to the region, he resisted cries for war with Britain and issued a proclamation of neutrality regarding the Canadian rebellion. In 1840 a Canadian, Alexander McLeod, was arrested in New York for the murder of the American killed in the Caroline affair but was later acquitted. British-American relations, aggravated further by the Aroostook War, remained strained until the signing of the Webster-Ashburton Treaty in 1842."