By Matt Rivers

PHILADELPHIA (CBS) – Missouri Governor Jay Nixon declared a State of Emergency and imposed a curfew Saturday as the unrest reignites in Ferguson following the shooting death of 18-year-old Michael Brown.

One week ago, Brown — an unarmed black teenager from Ferguson — was shot and killed by a police officer. Saturday there was a call for calm after protests turned violent again overnight.

“If we’re going to achieve justice, we must first have and maintain peace,” Nixon says.

From 12 a.m. to 5 a.m. each night, no one will be allowed on Ferguson’s streets. That was the announcement by Nixon late afternoon after days of protests, some violent, most peaceful.

“This is not to silence people of this region or others, but to contain those who are drowning out the voice of the people with their actions,” Nixon explained.

The press conference was extremely confrontational as both police and government officials were routinely shouted down by protesters.

“You need to charge that police with murder,” one protester said.

Members of the press did not have a chance to ask questions as members of the public called for a swift prosecution of Ferguson officer Darren Wilson, who shot Brown.The curfew announcement came after a day of marches and steady rain commemorating the one week anniversary of Brown’s death.

“The protest is to be silent,” this protester said. “Our heads uplifted, don’t shoot and our heads down in deference to parents who have lost their child.”

Shortly after midnight, officials said small groups of protesters turned violent. One canister of tear gas was deployed and three police officers were injured. The actions prompted the curfew announcement.

Friday, Ferguson police first identified officer Wilson as Brown’s shooter, but in that same press conference, they said Brown was a suspect in a convenience store robbery that happened minutes before his death. Police released video of the robbery showing a man who resembles Brown. Police said Brown was confronted ten minutes later by officer Wilson. Brown’s family challenged the timing of the announcement:

“The family feels that that was strategic,” says Brown family Attorney Anthony Gray. “They think it was aimed at denigrating their son. It was a character assassination attempt.”

And they say even if he did commit the crime, he did not deserve to die.

The FBI now has a heavy presence in the area, sending agents door to door to assist in the investigation into the shooting. Police also announced Saturday that the press will be given a staging area to ensure transparency in the process. Reporters’ access has been severely limited over the first few days of the protests.

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