Cincinnati was racked with fires and thrown rocks and bottles Wednesday as disturbances broke out after a white police officer was found innocent of charges related to the killing of an unarmed black man.

Mayor Charlie Luken clamped down on the city with an overnight curfew and a state of emergency, Lt. Kurt Byrd said.  The unrest was still less severe than the three days of violence after the shooting itself, in which dozens were arrested and 800 injured, rivaling the chaos in the city after the 1968 assassination of the Rev. Martin Luther King, Jr.

Officer Stephen Roach shot 17-year-old Timothy Thomas on April 7, setting off the initial burst of violence and months of racially charged tension in the city. Thomas, who was wanted on 14 warrants, was shot in the chest after running from three other police officers.

On Wednesday, Roach, 27, was acquitted by Hamilton County Municipal Judge Ralph E. Winkler on charges of negligent homicide and obstructing official business. About 12 hours later, violence erupted in Over the Rhine, the same crime-ridden neighborhood at the center of the April disturbances.

Cars were hit with rocks and bottles a block from where a vigil was being held for Thomas. At the vigil site, one photographer suffered minor injuries when he was struck on the foot with a brick. Another photographer was cut by glass from a broken bottle and taken to a hospital. At least two news vehicles were damaged. One car was set on fire, and there were at least six trash-can fires. One arrest was made, Byrd said.

Police called in backups and put all officers on 12-hour shifts because of the outbreak, but Byrd said most of the violence had subsided by the time the curfew was imposed.

"All the officers in the area are going to helmets and shields," said Byrd. "It's not been anything remotely close to what we had this spring. At this point, we think we can keep it under control."

Peaceful protests were held earlier in the day outside the courthouse and at City Hall after Roach was cleared by Judge Winkler.

Winkler, who heard the case without a jury at the officer's request, concluded that the shooting was "not a culpable criminal act" because Roach had been put into a situation where he believed he had to shoot, or else be shot himself.

"Police officers are often forced to make split-second judgments in circumstances that are tense, uncertain, dangerous and rapidly evolving," Winkler said. "Such was the case Officer Roach faced here."

Roach could have been sentenced to nine months in jail if convicted of both charges.  He still faces possible department discipline. He glanced down while the verdicts were read, and his wife, Erin, sobbed into her hands.

"I would give anything to change the outcome of what happened that night, but unfortunately I can't," Roach said outside the courtroom, holding hands with his wife.

Thomas' mother, Angela Leisure, said she still didn't believe it was necessary for Roach to shoot her son. She said Roach should have been convicted to send a message to a police department that has been accused of mistreating blacks.

"I wanted my son to be the last [to be shot] — but he won't be the last," Leisure said. "Until serious changes are made in our police department, this will happen again."

Eric Green, 32, a Cincinnati construction worker, said he expected violence might break out in response to the verdict.

"Meet force with force, meet fire with fire. There's nothing else to do to get our message across," Green said.

Black activists also expressed disappointment with the verdict.

"It was a travesty ... to let him walk," said the Rev. Damon Lynch III, a minister and black leader. "It set this city 10 steps back. Black life has no value in Cincinnati."

The Associated Press contributed to this report