UPDATE #3: Now all six officers are in custody, according to The Baltimore Sun.

UPDATE #2: According to NBC News, Baltimore Mayor Stephanie Rawlings-Blake says that five of the six officers have been taken into custody.

UPDATE: CNN provided a breakdown of the individual charges: 

One officer -- the driver of the police van -- has been charged with several counts, including second-degree depraved-heart murder. Another officer has been charged with several counts, including manslaughter and involuntary manslaughter. Two other officers have been charged with several counts, including involuntary manslaughter. An additional two officers are charged with several counts, including second-degree assault.

This letter from State's Attorney Marilyn Mosby includes the officer's names: 

Officials say that that Freddie Gray's autopsy report has been forwarded to a prosecutor, who ruled his death a homicide. Gray, 25, died last month after suffering severe spinal injuries while in the custody of Baltimore police. 

According to CBS Baltimore, the medical examiner has completed Gray's autopsy. It has since been sent to both the governor and the State's Attorney's office: 

In addition, WJZ sources indicated the Gray family will be briefed shortly on the findings. According to WJZ sources, the medical examiner will list the cause of death as trauma to the neck and spine.

Sources also indicate authorities now believe the trauma was suffered inside the police van Gray was being transported in.

This comes the day after the Baltimore Police Department announced that it had completed its initial investigation into Gray's death. Furthermore, the Associated Press reports the state's attorney called Gray's death a homicide and believes there is probable cause for charges. As a result, all officers have been charged: 

In addition a police union has requested a special prosecutor:

[via CBS Baltimore and Associated Press]