The judge in the case of a Baltimore police officer on trial over a death in custody has declared a mistrial after the jury was unable to reach a verdict.
Policeman William Porter is the first of six officers charged in the death of 25-year-old Freddie Gray.
The jury deliberated for three days, but could not come to an agreement on all four charges.
Police have been positioned around the city to prevent riots like those that erupted following Gray’s death.
Small crowds protested late Wednesday along streets lined with police officers. The situation was quiet at the intersection where the worst rioting happened in April as parts of West Baltimore were set on fire.
Homicides have soared and the pressure on city officials has been unrelenting since Baltimore City State’s Attorney Marilyn Mosby charged six officers in Gray’s death.
Judge Barry Williams said the jury - composed of seven black and five white people - had “clearly been diligent” in their deliberations.
The mistrial is a major setback for prosecutors, who may now have to build another case against the policeman. They had also hoped to use Mr Porter as a witness in the trials against the other five officers, had he been found guilty.
Gray died in hospital in April after spending about a week in a coma
Judge Williams has scheduled a hearing for Thursday to discuss a possible new trial.
Urging the public to remain calm, Gray’s family thanked the the jury for their service and pushed for the prosecutor to bring a new trial against Mr Porter.
After the announcement and into the evening, protesters marched through the streets and demonstrated in front of City Hall and other prominent buildings.
“Indict, convict, send those killer cops to jail,” some of the protesters chanted, during peaceful demonstrations.
The Baltimore neighbourhood that experienced the worst of April’s rioting after Gray’s funeral was calm in the hours after the mistrial of the first officer charged in Gray’s death.
Tessa Hill-Aston is president of the Baltimore branch of the NAACP. She took part in a prayer and unity gathering Wednesday night at the intersection that was the epicenter of April’s unrest.
She said people are expressing support for peace. Nearby, protesters peacefully called for justice and greater awareness of the community’s economic hardships.
Ms Hill-Aston said while a lot of people are upset that the trial of Officer William Porter ended in a mistrial, she said they recognise that they have a lot more to go through with five more trials of other officers charged in the case.