Story highlights Officer who fatally shot teen is identified as Darren Wilson, 28

Police say Michael Brown was prime suspect in a robbery just before police shooting

Witnesses, police concur that tussle preceded shooting, Brown was unarmed

Details in dispute as witnesses deny claim that Brown reached for officer's weapon

What really happened to Michael Brown?

We know a police officer in Ferguson, Missouri, fatally shot the unarmed 18-year-old , but police and witnesses have given different accounts of what happened in the moments before the shooting. The confusion has fueled protests in Ferguson and, earlier in the week, strong police response in the streets of the St. Louis suburb.

Here are five key questions about the incident:

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How did it start?

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Brown and Dorian Johnson, 22, were walking in the middle of the street, en route to either Brown's grandmother's house (according to Brown's mother and grandmother) or to Johnson's house (according to Johnson), when a Ferguson police officer confronted them.

Officer Darren Wilson, who is white, told the young men either "Get the f*** on the sidewalk" or "Get the f*** out of the street," according to Johnson's accounts to CNN and other news outlets.

The young men replied that they were "not but a minute away from our destination, and we would shortly be out of the street," Johnson told CNN.

The officer drove away but stopped and backed up, almost hitting the pair, Johnson said. He said he wasn't sure what prompted the officer to return. Johnson told MSNBC the officer said something to the effect of "What'd you say?"

"We were so close, almost inches away, that when he tried to open his door aggressively, the door ricocheted both off me and Big Mike's body and closed back on the officer," Johnson said.

A caller to the St. Louis radio program The Dana Show, on Radio America, gave what she said was the officer's version of events. Her account accurately matches what Wilson has told investigators, a source with detailed knowledge of the investigation told CNN.

The caller, who identified herself only as "Josie," said that Wilson told her that the two young men were walking in the street and he rolled down his window and told them to get out of the street.

Was there a struggle?

Yes. Everyone agrees on this point, and it's one of the few aspects of the shooting that police have attempted to detail , though the official explanation has spurred many questions they have yet to answer.

The preliminary investigation showed that the officer tried to exit his vehicle, but Brown pushed him back into the car, "where he physically assaulted the police officer" and struggled over the officer's weapon, St. Louis County Police Chief Jon Belmar said.

A shot was fired inside the police car, Belmar said. After the incident, the officer was taken to an area hospital, where he was treated for a "swollen face," according to Ferguson Police Chief Thomas Jackson.

In Josie's version, Wilson may have heard a call about a strong-arm robbery and saw the young men carrying something that might have been stolen cigars. According to Josie, when Wilson tried to get out of his car, Brown pushed him back in, and then punched the officer in the face. It was then that Wilson reached for his gun, Josie told the radio show.

Brown grabbed Wilson's gun, and the officer pushed it away and the gun went off, Josie said.

The stories don't jibe with at least three witness accounts.

Johnson claims the officer grabbed Brown by his neck , and Brown tried to pull away, but the officer kept pulling Brown toward him, he said.

The officer drew his weapon, and "he said, 'I'll shoot you' or 'I'm going to shoot' " and almost instantaneously fired his weapon, hitting Brown, Johnson said.

Witness Tiffany Mitchell was picking up coworker Piaget Crenshaw for their jobs when she saw Brown and the officer "tussling through the window." Mitchell and Crenshaw said Brown appeared to be trying to pry himself from the officer's grasp. Brown had his hand on the police cruiser, trying to push himself away, Mitchell said.

Was Brown armed?

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No. Again, this is undisputed.

Every casing found at the scene came from the officer's gun, Belmar said, and witnesses say that after the officer initially fired, the two young men took off running.

"I saw the officer proceeding after my friend, Big Mike, with his gun drawn, and he fired a second shot, and that struck my friend, Big Mike," Johnson said. "And at that time, he turned around with his hands up, beginning to tell the officer that he was unarmed and to tell him to stop shooting. But at that time, the officer was firing several more shots into my friend, and he hit the ground and died."

This matches Crenshaw's and Mitchell's story . Crenshaw told CNN that Brown got about 20 feet away from the police cruiser before the officer shot him again.

"The cop gets out of his vehicle shooting," Mitchell said. "(Brown's) body jerked as if he was hit from behind, and he turned around, and he put his hands up. ... The cop continued to fire until he just dropped down to the ground, and his face just smacked the concrete."

A private autopsy conducted for the Brown family showed that Brown had been shot at least six times, including twice in the head.

Josie, recounting the officer's version of events, told the radio program that after the first shot went off inside the car, Brown and his friend started running, and Wilson pursued as protocol dictates.

According to Josie, Wilson told the young men to freeze, and the pair turned around.

The officer's account is that Brown started to taunt him, saying he wouldn't shoot him, and then rushed at the officer at full speed, Josie said. It was then that Wilson started firing, Josie said.

She said that in the officer's opinion, Brown "was on something."

According to her, the final shot hit Brown in the forehead, and he fell two or three feet in front of the officer.

A new witness, Michael Brady, told CNN's Anderson Cooper on Wednesday that Wilson fired at Brown after the teen ran about 20 feet.

Brady ran out of his apartment to get a closer look.

Seconds later, he saw Brown doubled over, cradling one arm and beginning to fall forward. He took a step or two towards the officer but did not charge him, Brady said.

Wilson fired three to four more shots at him, he said.

What were Brown and Johnson doing before the incident?

On Friday, six days after the shooting, Ferguson police revealed that Brown was the "primary suspect" in the strong-arm robbery of a convenience store moments before he encountered police and was killed.

A store surveillance video shows a man pushing a clerk before walking out the front door with a box of Swisher Sweets cigars worth $48.99, according to information released by police.

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The Brown family lawyer, Benjamin Crump, said that the person in the video appears to be Michael Brown.

Johnson, who was with Brown when he was shot, will not face any criminal charges in connection with the store robbery because "we have determined he committed no crime," Jackson said.

Jackson initially said that the officer who shot Brown was responding to a call about the robbery.

Later, Jackson revised that comment, saying the officer approached Brown not because of the robbery, but because he was "walking down the middle of the street, blocking traffic."

Why didn't police identify the officer right away?

It took police six days to publicly identify Wilson.

Police initially promised to release the officer's name but held off, saying they feared for his safety.

On Friday, police revealed the officer as Wilson , 28, who is a six-year veteran of the department without any history of disciplinary action.

Wilson is on paid administrative leave, Belmar said, and will have to undergo two psychological evaluations before returning to duty.

Though the officer was promptly released from the hospital, Jackson said he spoke to him, and he was "very shaken about what happened that day and the aftermath. ... He's hurt."

Brown's family and their attorneys were infuriated that police released Wilson's identity and allegations of Brown's role in the robbery on the same day.

"The prolonged release of the officer's name and then the subsequent alleged information regarding a robbery is the reason why the family and the local community have such distrust for the local law enforcement agencies," the family and lawyers said in a statement.