Gov. Brigham Young issued a proclamation: "Citizens of Utah - We are invaded by a hostile force" without any investigation by the government. He declared his actions justified by "the great first law of self preservation and put the Territory of Utah under martial law, forbidding the troops to enter Salt Lake Valley. He ordered large numbers of armed militia to Echo Canyon and other points to intercept the soldiers and prevent their access to the Valley.
[Source: Hale, Van, Mormon Miscellaneous, Utah War Chronology, http://www.mormonmiscellaneous.com/utahwar/id2.html]