Gray, 25, was arrested in west Baltimore the morning of April 12, 2015, then placed in the back of a police van with his hands cuffed behind his back and his legs shackled. As he was being transported, he suffered a severe neck injury and lost consciousness. He died in the hospital about a week later.
The death sparked violent protests in Baltimore, and Baltimore State's Attorney Marilyn Mosby ultimately charged six officers involved in handling Gray with various state crimes. Meanwhile, the Justice Department launched its own criminal, civil rights investigation into Gray's death, as well as a broader probe of possible systemic violations in the Baltimore Police Department.
Michael Davey, who represents Lt. Brian Rice, the highest-ranking officer involved in Gray's arrest, said "We're very pleased that the Department of Justice has come to the conclusion they did." He said he only wished the local prosecutor had reached the same determination "prior to any of the criminal charges being placed."
Rice, along with Officers Caesar Goodson Jr., William Porter, Edward Nero, Garrett Miller and Sgt. Alicia White, were charged with various offenses in Gray's death, including manslaughter, assault and reckless endangerment. Goodson, who drove the van, was the sole officer charged with murder.
Mosby on July 27, 2016 dropped criminal charges against White, Miller and Porter. Three other officers - Goodson, Rice and Nero - were found not guilty after separate trials. Porter had gone to trial once, but the proceeding ended in a mistrial.
The Justice Department said it had conducted a comprehensive, independent investigation of the events, reviewing surveillance footage, witness interviews, medical reports and other materials. Prosecutors, the Justice Department said, considered several different legal violations, "including theories of false arrest, excessive force, and deliberate indifference to the risk of serious harm to Gray."
The investigation included an assessment of whether Gray should have been arrested in the first place, whether Goodson gave Gray a "rough ride" and an analysis of officers' failure to seatbelt Gray, among many other things.
Even where prosecutors may have found some fault - Goodson, for example, made a wide right turn and crossed a double yellow line, and Gray was not buckled in per department policy - they could not substantiate criminal wrongdoing, the Justice Department said. The department said evidence "overwhelmingly contradicted reports from some civilian witnesses that Gray was either tased or beaten by the officers."
The officers could still face professional repercussions. Davey, the attorney who represents Rice, said that internal disciplinary hearings are scheduled to begin for five of the six officers in October. Porter is not facing any internal charges. The hearings are public.
The Baltimore department, too, is still broadly working to implement reforms. The Justice Department during the Obama administration had found that the Baltimore police officers used excessive force and disproportionately stopped African-Americans, and ultimately reached an agreement with the city to institute reforms.
Attorney General Jeff Sessions, though, has taken a markedly different stance on police reform than his predecessors, and he has been particularly critical of broad, court-enforceable agreements to mandate police departments undergo change. His Justice Department tried to delay the reform agreement in Baltimore, though a judge ultimately approved it over federal authorities' objection.
Sessions seems to be more amenable to charging individual officers with wrongdoing, though - like his predecessors - he has found that doing so is not easy under federal law. The Justice Department announced in May that it would not bring charges against the police officers involved in the death of Alton Sterling, whose fatal shooting in Baton Rouge last summer was captured on a video that rocketed around social media.
More recently, the Justice Department closed without charges its investigation into the death of 19-year-old Michael Moore, who was fatally shot by an officer in Alabama in 2016.
The Justice Department is still probing the high-profile death of Eric Garner, who died in 2014 after he was taken to the ground by New York City police officers. His death was also caught on video, sparking national outrage and helping coin the rallying cry, "I can't breathe.