Updated

The beleagured chief of the Ferguson, Missouri, police department, Thomas Jackson, identified at last on Friday the name of the officer who shot an unarmed black teenager which has ignited days of heated protests.

He also released documents alleging that 18-year-old Michael Brown, who was shot by a police officer named Darren Wilson, was the primary suspect in a store robbery. Police allege that Brown and a friend, Dorian Johnson, intimidated a store clerk and made off with $48.99 worth of cigars.

Officer Wilson has been on administrative leave since the shooting on Aug. 9.

Jackson said Wilson, along with other officers, was called to the area that day after a 911 call reporting a "strong-arm" robbery just before noon. He said a dispatcher gave a description of the robbery suspect, and Wilson, who had been assisting on another call, was sent to investigate.

Wilson, a six-year veteran of the police department, encountered Brown just after 12:01 p.m., with a second officer arriving three minutes later, Jackson said.

Brown's death has sparked several days of clashes with furious protesters in the city. The mood was quelled on Thursday, after the governor turned oversight of the protests to the state Highway Patrol. State troopers walking side-by-side with thousands of peaceful protesters replaced the county police in riot gear and armored tanks of previous nights.

But the police chief's announcement Friday was met with immediate disbelief and anger by several dozen community members who also attended the news conference, which was hastily held at a gas station burned during a night of looting earlier in the week.

"He stopped the wrong one, bottom line," yelled Tatinisha Wheeler, a nurse's aide who was at the news conference.

A couple dozen protesters began marching around the area and in the street chanting, "Hands up, don't shoot," and, "What do we want? Justice! When do we want it? Now!"

Police have said Brown was shot after an officer encountered him and another man on the street. They say one of the men pushed the officer into his squad car, then physically assaulted him in the vehicle and struggled with the officer over the officer's weapon. At least one shot was fired inside the car before the struggle spilled onto the street, where Brown was shot multiple times, according to police.

Dorian Johnson has told media very different story. He has said he and Brown were walking in the street when an officer ordered them out of the street, then grabbed his friend's neck and tried to pull him into the car before brandishing his weapon and firing. He said Brown started to run and the officer pursued him, firing multiple times.

Tensions boiled over after a candlelight vigil Sunday night, as looters smashed and burned businesses in the neighborhood, where police have repeatedly fired tear gas and smoke bombs.

But on Thursday, county police in riot gear and armored tanks gave way to state troopers walking side-by-side with thousands of peaceful protesters. The dramatic shift came after Gov. Jay Nixon assigned oversight of the protests to the state Highway Patrol, stripping that authority from the St. Louis County Police Department.

"All they did was look at us and shoot tear gas," Pedro Smith, who has participated in the nightly protests, said Thursday. "This is totally different. Now we're being treated with respect."

The more tolerant response came as President Barack Obama spoke publicly for the first time about the shooting — and the subsequent violence that shocked the nation and threatened to tear apart Ferguson, a town of 21,000 that is nearly 70 percent black and patrolled by a nearly all-white police force.

Obama said there was "no excuse" for violence either against the police or by officers against peaceful protesters.

Nixon's promise to ease the deep racial tensions was swiftly put to the test as demonstrators gathered again Thursday evening. But the latest protests had a light, almost jubilant atmosphere among the racially mixed crowd, more akin to a parade or block party.

The streets were filled with music, free food and even laughter. When darkness fell — the point at which previous protests have grown tense — no uniformed officers were in sight outside the burned-out QuikTrip convenience store that had become a flashpoint for standoffs between police and protesters.

"You can feel it. You can see it," protester Cleo Willis said of the change Thursday. "Now it's up to us to ride that feeling."

Nixon appointed Highway Patrol Capt. Ron Johnson, who is black, to lead the police effort. Johnson, who grew up near Ferguson and commands a region that includes St. Louis County, marched alongside protesters Thursday, joined by other high-ranking brass from the Highway Patrol as well as the county department. The marchers also had a police escort.

"We're here to serve and protect," Johnson said. "We're not here to instill fear."

Attorney General Eric Holder has said federal investigators have interviewed witnesses to the shooting.

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