WASHINGTON — Twelve people, including three U.S. Army soldiers, are accused in a large-scale gun trafficking ring that prosecutors allege supplied nearly 100 guns to gang members in Chicago and led to at least two killings, the Justice Department said Friday. The soldiers — Demarcus Adams, 21; Jarius Brunson, 22; and Brandon Miller, 22 — were enlisted in the Army and stationed at Fort Campbell in Kentucky, where they would legally purchase guns from local dealers in Tennessee and Kentucky, prosecutors charged. The …