(FERGUSON, Mo.) — Officer Darren Wilson said Michael Brown "had the most intense aggressive face I've ever seen on a person," when the unarmed 18-year-old turned to face him after the two struggled in Wilson's patrol car, and the teen kept coming at him even after he'd shot him multiple times.

"After I fired multiple shots I paused for a second, yelled at him to get on the ground again, he was in the same state. Still charging in, hands still in his waistband," Wilson told police investigators the morning after the fatal shooting.

"I fired another set of shots. Same thing, still running at me, hadn't slowed down, hands still in his waistband," Wilson said. "He gets about eight to 10 feet away, he's still coming at me in the same way. I fired more shots. One of those, however many of them, hit on him in the head and he went down right there."

Wilson's account was part of the evidence presented to the grand jury that investigated the Aug. 9 shooting.

The evidence was released by the St. Louis County prosecutor Monday evening after the grand jury declined to indict Wilson.

Wilson said he had heard that someone had stolen cigarillos from the nearby Ferguson Market just before he saw two young men walking in the middle of the street, disrupting traffic.

He said that after he asked the two to move onto the sidewalk, one said, "F*** what you have to say," as they passed him.

"When he said that, it drew my attention totally to Brown," he said. "It was a very unusual and not expected response from a simple request."

Then he noticed that Brown was carrying packages of cigarillos, which had been reported stolen, he said.

He called for backup and then backed up his car to cut them off, he said. When he started to open the door and called to Brown, the young man responded: "What the f*** are you gonna do?" he said.

The officer told investigators that when he tried to open the door, Brown slammed it shut.

"He was just staring at me, almost like to intimidate me or to overpower me," Wilson said. "The intense face he has was just not what I expected."

Wilson said he tried to open his door again, telling Brown to "get the f*** back," but Brown grabbed the door and slammed it, then ducked his head inside the open window.

"I don't remember seeing him come at me, but I was hit right here in the side of the face with a fist," Wilson said. "I think it was a full-on swing, but not a full shot."

When Brown turned to give the cigarillos he was carrying in his left hand to the other young man, Wilson tried to grab his right "to get out, to have some type of control and not be trapped in my car anymore," he said.

"And when I grabbed him, the only way I can describe it is I felt like a 5-year-old holding onto Hulk Hogan," he said.

As the two struggled, with Wilson seated inside the car and Brown leaning in through the open window, he tried to get his mace canister but couldn't reach it, according to the officer's account.

"I thought I was already compromised enough. I drew my firearm, I pointed at him," Wilson said.

He said that when he warned Brown he was going to shoot him and told him to get on the ground, the teen grabbed the gun and said, "You are too much of a p***y to shoot me."

"When he grabbed my gun, he twisted it, pointed at me and into my hip pelvic area," he said.

"I know his hand was around my trigger finger which was inside the trigger guard, and when he grabbed it he pushed it down and angled it to where it was like this in my hip," Wilson said. "I was guaranteed he was going to shoot me."

Brown had "completely overpowered" him, Wilson said, but he was able to twist the gun around and get a shot off, and then another, but he didn't know what he had hit.

"It was a, just one of these to get him off me," Wilson said.

He said he radioed for more patrol cars, then yelled for Brown, who was running then, to stop and get on the ground.

Brown stopped, but he didn't get down, Wilson said.

"When he stopped, he turned, looked at me, made like a grunting noise and had the most intense aggressive face I've ever seen on a person," Wilson said.

Copyright 2014 ABC News Radio  (PHOTO: Michael Brown Family/Facebook)