WASHINGTON, Sept. 12 (Xinhua) -- The U.S. Department of Justice won't bring federal charges against six police officers involved in the in-custody death of a young black man, it was revealed on Tuesday.

The 2015 death of Freddie Gray, 25, has triggered weeks of protests against police brutality and turmoil in the city of Baltimore, the state of Maryland.

Gray was handcuffed, shackled but unrestrained by a seat belt when his neck was broken in the back of a police transport wagon on April 12, 2015. He suffered a fatal spinal cord injury and eventually died one week after.

Six police officers were charged by state prosecutors after Gray's death. Three of them were acquitted at trial, and Baltimore State's Attorney Marilyn Mosby later dropped the remaining state cases.

The Gray family's attorney, Billy Murphy, said the Justice Department informed him on Tuesday that no federal charges would be filed. The decision means none of the officers will be held criminally responsible for Gray's death.

However, five officers face internal disciplinary hearings scheduled to begin on Oct. 30. The sixth one was not charged administratively, according to reports from the Baltimore Sun newspaper and ABC News.

Amid the escalated unrest and violence following Gray's funeral on April 27, 2015, the then U.S. Attorney General Loretta Lynch announced that the Justice Department would be launching a federal civil rights investigation into his death.