Published: Feb 11, 2014 1:04 PM EST

JACKSONVILLE, Fla. (AP) - The Florida man charged with fatally shooting a 17-year-old boy after an argument over loud music testified Tuesday that he thought he saw the barrel of a gun from a neighboring vehicle pointed at him and that he feared for his life in the moments before he fired his weapon.
    
Michael Dunn said he tried to de-escalate the confrontation with three teens in a neighboring SUV outside a Jacksonville convenience store in November 2012.
    
"I couldn't believe what I was seeing and hearing," Dunn said.
    
Dunn is charged with first-degree murder. He has pleaded not guilty and says he acted in self-defense when he fatally shot 17-year-old Jordan Davis of Marietta, Ga., outside a Jacksonville convenience store in 2012.
    
Dunn told jurors he was in Jacksonville with his fiancee to attend his son's wedding. He had brought along on the trip his 7-month-old dog, and at one point in testimony he wiped away tears when talking about his fiancee and dog.
    
Dunn said he and his fiancee went to the convenience store after the wedding for wine and chips. He said he pulled into a spot next to an SUV where music with a "thumping" bass was playing.
    
"It got really loud," Dunn said. "My rear view mirror was shaking. My eardrums were vibrating. It was ridiculously loud."
    
Dunn said he asked the three men in the SUV to turn down the music and they turned off the music. "I said, 'Thank you,'" Dunn said. But soon afterward, Dunn said he heard someone in the SUV shouting expletives at him and the word "cracker."  Dunn is white and the teens in the SUV were black.
    
The music was turned back on with a thumping bass. Dunn said when the music was turned back on "I wasn't going to ask for favors anymore."
    
Dunn said the men in the SUV had "menacing expressions" and he asked the teens if they were talking about him. He said he wanted to de-escalate the situation but he saw a teen in the backseat reach down for something which he slammed into the car door. Dunn said it looked as if the barrel of a shotgun was sticking out the window.
    
One of the teens stepped out of the SUV, Dunn said, and he felt "this was a clear and present danger." He reached for his pistol in a glove box.
    
Dunn, who had a concealed weapons permit, fired nine shots into the car, according to an affidavit.
    
No weapons were found in the SUV.
    
Prosecutors rested their case Monday, a week after jury selection began.
    
Before Dunn took the stand, Circuit Judge Russell Healey rejected a defense request to have a family counselor testify about how the stress Dunn suffered during the encounter explains his actions.

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