Meanwhile, the United States Secretary of War, Simon Cameron, had sent a letter to Lyon, the temporary commander of the arsenal, authorizing him to raise more companies of Union soldiers. It was endorsed by President Abraham Lincoln and Lieutenant general Winfield Scott. On May 10, 1861, Lyon surrounded the camp of the Missouri Militia and arrested all of the members. He marched his prisoners through the streets of St. Louis to the arsenal. When Southern sympathizers in St. Louis started a riot, Lyon quickly put it down. Many of the rioters were killed.