By Michelle Watson, CNN(CNN) — Ian Roberts, the leader of Des Moines’ schools who was detained by immigration agents last week, is resigning, his lawyer said Tuesday. “We will today be sending a letter to the Des Moines school board authorized by Dr. Roberts to resign his position as the superintendent of Des Moines public schools,” his attorney Alfredo Parrish said during a news conference. He was placed on paid and then unpaid leave by the Des Moines School Board. Parrish said his office filed a motion to stay Monday for Roberts’ case, and he was in the process of filing a motion to reopen the case as of Tuesday. Justice Department opens investigationThe Justice Department opened a civil rights investigation into Des Moines Public Schools (DMPS) over its employment practices, the agency said in a news release Tuesday.