Updated

The judge announced a mistrial Wednesday in the case of the first officer charged in the death of Freddie Gray, after jurors in Baltimore announced they could not reach a unanimous decision.

Jurors deadlocked on all four counts: manslaughter, assault, reckless endangerment and misconduct in office. After notifying Circuit Judge Barry Williams, he dismissed them, saying, "You have taken the time to listen."

Wednesday marked the third day of deliberations in the case of William Porter, one of six officers charged in Gray's death.

Three black men, four black women, two white men and three white women made up the jury. Gray was black. Porter is also black, as are two of the other five officers charged.

After court adjourned, Porter conferred solemnly with defense attorney Joseph Murtha and walked from the courtroom. A female supporter joined Porter on a marble bench in a corner of the hallway. Courthouse deputies blocked reporters from approaching them.

Murtha declined comment, citing a judicial gag order. Baltimore City State's Attorney Marilyn Mosby, who brought charges against six officers in the arrest and death of Gray, also declined comment.

A retrial date will be set Thursday. The charges carried maximum prison terms totaling 25 years.

Prosecutors say Porter is partly responsible for failing to buckle Gray into a seatbelt and for not calling an ambulance when Gray indicated he was in distress. Porter told jurors that he didn't think Gray was injured and that it was the van driver's responsibility to fasten Gray's seat belt.

A small group of protesters was seen outside the courthouse chanting "send those killer cops to jail," after the judge declared the mistrial. The sheriff called it an unlawful assembly, and at least one protester was arrested.

Fox News is told FBI's Baltimore field office and the Bureau of Alcohol, Tobacco, Firearms and Explosives are closely monitoring the situation and stand ready to assist local authorities if requested. Fox News has learned that FBI assets will not be used for any crowd control type operations, but that they could be called upon for any number of things to include intelligence and monitoring support.

The Special Agent in Charge of ATF's Baltimore field office has been in direct contact with the Baltimore police commissioner. Fox News is told that ATF stands ready to provide agents to command centers - if one is established - and agents for investigations at the request of local authorities.

Maryland's Department of Public Safety and Correctional Services had announced earlier Wednesday it was preparing for new protests and arrests that may take place. "We have relocated some detainees at the Baltimore Central Booking and Intake Center," Communications Director Robert Thomas said.

"As a unified city, we must respect the outcome of the judicial process," Mayor Stephanie Rawlings-Blake said in a statement. "In the case of any disturbance in the city, we are prepared to respond. We will protect our neighborhoods, our businesses and the people of our city."

Baltimore Police Commissioner Kevin Davis described the mistrial as "part of the process of the justice system. He added that Poter remains suspended without pay.

When asked during a press briefing if Baltimore police were aware of any messages on social media inciting violent protests, Davis said there was "nothing to concern us" as of Wednesday.

NAACP National President and CEO Cornell William Brooks called for continued protests "while using all of the available nonviolent means to seek justice for a violent death."

"While we respect the legal process and still await justice, the death of Freddie Gray and other tragedies continue to point to the need for systemic reform both within the municipal police departments and statewide,"he said in a statement.

The jurors had made several requests since they began deliberating Monday. The judge granted some and denied others, saying they were not part of the evidence. On Wednesday, they asked for a copy of a transcript from a witness, but the judge refused.

“When Officer Porter began this journey through the judicial process, we asked that everyone allow him his day in court as is promised to all citizens," Gene Ryan, president of the Fraternal Order of Police Lodge No. 3, which represents Baltimore police officers, said in a statement.

"Seven months later, Officer Porter is no closer to a resolution than he was at that time. Our legal system, however, allows for outcomes of this nature, and we must respect the decision of the Jury, despite the fact that it is obviously frustrating to everyone involved."

Fox News' Matt Dean, Jake Gibson and The Associated Press contributed to this report.