FERGUSON, Missouri — The last moments of Michael Brown’s life were filled with shock, fear and terror, says a witness who stood just feet away as a police officer shot and killed the unarmed teen.

“I saw the barrel of the gun pointed at my friend,” said Dorian Johnson, 22. “Then I saw the fire come out of the barrel.”

Johnson, in an exclusive interview with msnbc, said what began as an order by a police officer to ‘get the f— onto the sidewalk’ quickly escalated into a physical altercation and then, gunfire.

Close video Second night of unrest in Missouri Angry protesters and police face off in a St. Louis suburb over the killing of an unarmed teenager Michael Brown. Ron Allen and community activist James Clark join. Angry protesters and police face off in a St. Louis suburb over the killing of an unarmed teenager Michael Brown. Ron Allen and community activist James Clark join. share tweet email Embed

Johnson says he feared for his life as he watched the officer squeezing off shot after shot.

“I could see so vividly what was going on because I was so close,” said Johnson, who said he was within arm’s reach of both Brown and the officer when the first of several shots was fired at the teen.

Brown’s killing on Saturday afternoon has sparked protests and rioting in this small, hardscrabble suburb of St. Louis, where tensions continue to rise between the police and the largely black, mostly poor community. Brown’s shooting lifted the lid on a pot that had long been bubbling .

The police say the officer shot Brown after the teen shoved the officer and tried to wrestle the officer’s gun from him. But a number of witnesses, including Johnson, refute those claims. And in the wake of the shooting, the Ferguson Police Department has asked the St. Louis County police to step in and take over the investigation.

Meanwhile, the identity of the police officer involved in the shooting has not yet been identified. It is known, however, that the officer who shot Brown has been placed on paid administrative leave.

But as darkness fell over Ferguson on Monday, ongoing protests were stifled by rubber bullets and tear gas fired at protesters by officers, according to witnesses.

Related: Witness: Brown did not reach for officer’s weapon

Local branches of the NAACP have called on the Justice Department and federal and state law enforcement officials to take over the investigation from local police. The FBI has joined the investigation and the Justice Department has said it is keeping an eye on the case. Attorney General Eric Holder on Monday said that the FBI will help local authorities undertake a “thorough, fair investigation.”

For its part, Brown’s family has hired local attorney Anthony Gray and Benjamin Crump, a civil rights attorney who represented the family of Trayvon Martin.

“That baby was executed in broad daylight,” Crump said during a press conference Monday afternoon, standing beside Brown’s mother and father. Crump told a crowd of several dozen that Brown was shot and left in the road like an animal.

“He was a good boy who didn’t deserve any of this,” said Michael Brown Sr., the teen’s father.

“I just wish I could have been there to help my son,” the boy’s mother, Leslie McSpadden said through tears.

“We can’t even celebrate because we have to plan a funeral.” Leslie McSpadden, mother of Michael Brown

On Monday, McSpadden and Brown’s father had planned to drop Brown off at a nearby technical college for the start of his freshman year. Instead, the family is making burial arrangements.

“We can’t even celebrate because we have to plan a funeral,” McSpadden said.

Johnson, who said he moved into the neighborhood about eight months ago, said he met Brown three months ago and the two became fast friends.

“Everyone else’s mentality be on some nonsense, silliness,” Johnson said. “But Mike had his mind set on more than that, helping others. I just got a good feeling from being around him.”

About 20 minutes before the shooting, Johnson said he saw Brown walking down the street and decided to catch up with him. The two walked and talked. That’s when Johnson says they saw the police car rolling up to them.

The officer demanded that the two “get the f—k on the sidewalk,” Johnson says. “His exact words were get the f—k on the sidewalk.”

After telling the officer that they were almost at their destination, Johnson’s house, the two continued walking. But as they did, Johnson says the officer slammed his brakes and threw his truck in reverse, nearly hitting them.

Now, in line with the officer’s driver’s side door, they could see the officer’s face. They heard him say something to the effect of, “what’d you say?” At the same time, Johnson says the officer attempted to thrust his door open but the door slammed into Brown and bounced closed. Johnson says the officer, with his left hand, grabbed Brown by the neck.

“I could see the muscles in his forearm,” Johnson said. “Mike was trying to get away from being choked.”

“They’re not wrestling so much as his arm went from his throat to now clenched on his shirt,” Johnson explained of the scene between Brown and the officer. “It’s like tug of war. He’s trying to pull him in. He’s pulling away, that’s when I heard, ‘I’m gonna shoot you.’”

At that moment, Johnson says he fixed his gaze on the officer to see if he was pulling a stun gun or a real gun. That’s when he saw the muzzle of the officer’s gun.

“I seen the barrel of the gun pointed at my friend,” he said. “He had it pointed at him and said ‘I’ll shoot,’ one more time.”

A second later Johnson said he heard the first shot go off.

“I seen the fire come out of the barrell,” he said. “I could see so vividly what was going on because I was so close.”

Johnson says he was within arm’s reach of both Brown and the officer. He looked over at Brown and saw blood pooling through his shirt on the right side of the body.

“The whole time [the officer] was holding my friend until the gun went off,” Johnson noted.

Brown and Johnson took off running together. There were three cars lined up along the side of the street. Johnson says he ducked behind the first car, whose two passengers were screaming. Crouching down a bit, he watched Brown run past.

“Keep running, bro!,” he said Brown yelled. Then Brown yelled it a second time. Those would be the last words Johnson’s friend, “Big Mike,” would ever say to him.

Brown made it past the third car. Then, “blam!” the officer took his second shot, striking Brown in the back. At that point, Johnson says Brown stopped, turned with his hands up and said “I don’t have a gun, stop shooting!”

Close video ‘I should be celebrating … but we’re planning a funeral’ Rev. Al Sharpton talks to Lesley McSpadden and Les McSpadden, the mother and grandfather of Michael Brown, to discuss Brown’s fatal shooting and denounce the violent protests that have followed in Ferguson, Missouri. Brown family attorney, Benjamin Crump, share tweet email Embed

Johnson described watching Brown go from standing with his hands up to crumbling to the ground and curling into a fetal position.

By that point, Johnson says the officer and Brown were face-to-face. The officer then fired several more shots.

“After seeing my friend get gunned down, my body just ran,” he said. He ran to his apartment nearby. Out of breath, shocked and afraid, Johnson says he went into the bathroom and vomited. Then he checked to make sure that he hadn’t also been shot.

Five minutes later, Johnson emerged from his apartment to see his friend Mike dead and in the middle of the street. Neighbors were gathering, some shouting, some taking pictures with their cell phones.

Freeman Bosley, Johnson’s attorney, told msnbc that the police have yet to interview Johnson. Bosley said that he offered the police an opportunity to speak with Johnson, but they declined.

“They didn’t even want to talk to him,” said Bosley, a former mayor of St. Louis. “They don’t want the facts. What they want is to justify what happened … what they are trying to do now is justify what happened instead of trying to point out the wrong. Something is wrong here and that’s what it is.”

Related: Follow Trymaine Lee’s reporting on the ground in Ferguson, Missouri

Johnson says he understands why the tension has boiled over into violence. As the protests seeking justice in Brown’s death have grown larger and more volatile, Johnson says he has joined them.

“There are two crowds. An older crowd that wants justice but there’s anger. Then it’s the younger crowd that wants revenge but there’s anger there, too,” Johnson said. “What do you expect when something is steadily occurring and its hurting the community and nobody is speaking out or doing anything about it. I feel their anger, I feel their disgust.”