The exact circumstances of what happened when a Missouri police officer shot and killed Michael Brown, an unarmed teenager, remain largely unknown.

Police have said that Brown was shot following a physical confrontation with an officer that included a struggle over the officer’s gun. Witnesses say that Brown, who police say was shot and killed 35 feet from the officer’s car, was shot as he was trying to surrender after an encounter initiated by the police.

Dorian Johnson, who said he was with Brown at the time of his death, told MSNBC in an interview that he was “shocked” at the officer’s actions on that street in suburban St. Louis.

Johnson told the network that the officer ordered them to “get the [expletive] onto the sidewalk.” They told the officer they were almost at their destination and kept going, but the officer hit his brakes and drove in reverse before confronting them.

“I feared for my life,” Johnson said. “I didn’t know what to do … My body really couldn’t move at that moment.”

Brown was “a very cool person,” Johnson said. “Quiet, calm and gentle.”

Johnson, who described himself as being within reaching distance of both the officer and Brown during the confrontation, said Brown did not “touch the officer in any type of a threatening way.” And Johnson disputed the police’s contention that Brown had struggled for the officer’s gun.

“He did not reach for a weapon at all,” he said. “He did not reach for the officer’s weapon at all.”

The entire episode unfolded very quickly, taking less than a minute, Johnson said.

Police have confirmed that Brown was shot multiple times. They have also said that the only shell casings recovered at the scene came from the officer’s gun.

Johnson had told KMOV, a St. Louis TV station, that the officer approached Brown and continued to shoot even after the teenager had his hands in the air.

Brown’s family and its attorney, Benjamin Crump, have asked for any eyewitnesses with video recordings of what happened to come forward. Johnson told MSNBC that he didn’t see anyone else in the immediate vicinity at the time.

Watch the full interview here.