Three days later Union Army Maj. Gen. Benjamin Butler, the commander of the Union ground forces, heard about the incident and decided to arrest and punish Mumford. When the Union Army occupied the city on May 1, Mumford was arrested and charged with "high crimes and misdemeanors against the laws of the United States, and the peace and dignity thereof and the Law Martial." On May 30, he was tried before a military tribunal and convicted, even though there was no clear attempt to determine whether the city was actually occupied when the event occurred.