Ferguson, Missouri, police Officer Darren Wilson, in his first interview since he fatally shot unarmed teenager Michael Brown, said he's not tormented by that fateful encounter on a street in suburban St. Louis last summer.

"I don't think it's haunting," Wilson told ABC News on Tuesday. "It's always going to be something that happened. The reason I have a clean conscience is that I know I did my job right."

Repeating what he told a grand jury investigating the shooting, Wilson said Brown reached into his police vehicle and grabbed for his gun. He feared for his life, he said.

It all started when Wilson asked the teenager to move out of the middle of the street, the officer told ABC's George Stephanopoulos. Brown walked over to his car and pushed the door back as Wilson tried to get out, the officer said.

"As I looked back at him, punches started flying," Wilson said in the interview, which aired Tuesday night. "He threw the first one and hit me in the left side of my face."

Wilson doesn't know how many times he got hit.

"I just know there was a barrage of swinging and grabbing and pulling for about 10 seconds," Wilson told ABC. "I reached out my window with my right hand to grab on to his forearm."

Wilson said he wanted to move Brown away.

"I just felt the immense power that he had. And then the way I've described it is, it was like a 5-year-old holding onto Hulk Hogan. That's just how big this man was," Wilson said. "He was very large, very powerful man."

Wilson is 6-foot-4 and 210 pounds; Brown was the same height and weighed nearly 300 pounds.

Brown unleashed another punch and struck the officer in his face, Wilson said.

"How do I survive," Wilson recalled thinking. "I didn't know if I'd be able to survive another hit like that."

Wilson reached for his gun and told Brown to back off or he would shoot, the officer said.

"You're too much of a (word bleeped) to shoot me," Wilson said Brown told him, before grabbing the top of the officer's gun.

Wilson tried to squeeze off two shots but the gun jammed twice.

Brown, he said, tried to reach the trigger guard to shoot Wilson. Wilson got a shot off on his third attempt, he said.

"He gets even angrier," Wilson said. "His aggression, his face, the intensity just increases. He comes back in at me again."