The other suspended officers were identified as:
- Lt. Brian Rice, 41, with the department since 1997.
- Sgt. Alicia White, 30, with the department since 2010.
- Officer Caesar Goodson, 45, who has been there since 1999.
- Officers William Porter and Edward Nero, who along with Miller, all joined in 2012.
Their specific roles in the arrest were not released.
Police Commissioner Anthony Batts said the reason for Gray's stop is "a question we have to dig into."
Billy Murphy, the lawyer hired by Gray's family, said he believes the officers had no probable cause to stop Gray.
"They've made concessions on lack of probable cause," Murphy said. "Running while black is not probable cause. Felony running doesn't exist, and you can't arrest someone for looking you in the eye. You have to believe he committed a crime and have an objective basis for that belief. They had none of that."
Gray's death has prompted daily protests and a vigil was planned Tuesday evening at the spot where he was arrested.
The death comes six months after Baltimore officials released a plan to reduce police brutality and misconduct. The plan followed a request by city officials to the U.S. Justice Department to review police policies and procedures.
The Justice Department's review should include a broad investigation of whether officers have committed civil rights violations, said the Rev. Cortly C.D. Witherspoon, president of the Baltimore chapter of the Southern Christian Leadership Conference. He said he plans to send a letter with that request by Wednesday.
Officials on Monday vowed transparency and pledged to hold those found responsible accountable. Batts said the investigation will be completed by May 1 and the results will be sent to the state attorney's office to determine whether criminal charges will be filed. Batts also said he is ordering that police review and rewrite "effective immediately" its policies on moving prisoners and providing them with medical attention.
"I understand the community's frustration. I understand it because I'm frustrated," Rawlings-Blake said. "I'm angry that we are here again, that we have had to tell another mother that their child is dead. I'm frustrated that not only that we're here, but we don't have all of the answers. I want to know why the officers pursued Mr. Gray. I want to know if the proper procedures were followed."
Police on Monday released a more detailed timeline of how Gray was arrested and transported.
It revealed that Gray was placed in leg irons after an officer felt he was becoming "irate" in the back of the transport van, and that the van made several stops on its way to the police station, even picking up another prisoner in an unrelated case, after Gray had asked for medical attention several times. Upon arrest, police said Gray asked for an inhaler and requested care several times before he was ultimately taken to the hospital.