Answer:
1. Because John Brown led a small group of armed slaves to raid against a federal armory in Virginia, an attempt to start a revolt and to destroy institutional slavery, such as slaveholding businesses, churches, schools, and other places in Virginia.
2. After the revolt, the U.S. sent soldiers to Virginia to arrest the raiders. After the U.S. arrested John Brown, he was tried for murder, treason, slave insurrection against the State of Virginia, and was hanged on December 2, 1859.