The U.S. Department of Justice is digging in deeper in Ferguson, Mo., initiating a civil rights investigation of the police department that follows the Aug. 9 fatal shooting of an unarmed black teen, Attorney General Eric Holder Jr. said last week.

Civil Rights Division lawyers will investigate whether the police department “engaged in systemic violations of the Constitution or federal law,” according to a Justice Department statement. The department already had opened a separate criminal civil rights investigation into the shooting death of 18-year-old Michael Brown by a Ferguson police officer. During a Sept. 4 news conference, Holder said he heard from residents during a visit to Ferguson two weeks earlier about the “deep mistrust” between the community and law enforcement, according to prepared remarks the department provided.