WASHINGTON — The United States Justice Department plans to open an investigation into the practices of the Ferguson Police Department following an officer's shooting last month of an unarmed black teenager in the Missouri town, a person briefed on the matter said Wednesday night.

The person said the investigation could be announced as early as Thursday. Missouri officials were notified Wednesday of the investigation.

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The investigation will look at the police department's practices, including stops, arrests and use of force, as well as the training that officers receive, the person said.

The investigation is separate from an ongoing civil rights investigation that the Justice Department is conducting into the fatal Aug. 9 shooting of 18-year-old Michael Brown by Ferguson police officer Darren Wilson. A local grand jury is also investigating the shooting, which set off nearly two weeks of unrest in the St. Louis suburb, and became a flashpoint in the national discussion of police treatment of minorities across the country.

Two weeks ago, Attorney General Eric Holder visited Ferguson, where he sought to reassure residents about the Justice Department investigation, and shared personal experiences of having been mistreated by police.

The person spoke on condition of anonymity because the investigation, first reported by The Washington Post, had not yet been announced.

Police have said a scuffle broke out after Wilson, who is white, told Brown and a friend to move out of the street and onto a sidewalk. Police say Wilson was pushed into his squad car, and physically assaulted. Some witnesses have reported seeing Brown's arms up in the air before the shooting, an apparent sign of surrender. An autopsy paid for by Brown's family concluded that he was shot six times, twice in the head.

Ferguson Police Chief Tom Jackson did not immediately respond to a request for comment.

The Justice Department's civil rights division routinely investigates individual police departments when there are allegations of systemic abuse or other problems. For instance, the department issued a scathing report in April that faulted police in Albuquerque, New Mexico, for a pattern of excessive force, and called for the police to overhaul its internal affairs unit and change policies on deadly encounters.

Many of the investigations end with a federal mandate to make significant changes to policies and practices.

A police officer who pointed a rifle at Ferguson protesters last month, and said he would kill them, resigned last Thursday. Lt. Ray Albers worked for the nearby St. Ann police department for 20 years.

Additional reporting by Mashable