According to authorities, an argument began after the 47-year-old Dunn told Davis and his friends to turn the music down they were listening to in an SUV outside the store. One of Davis' friends lowered the volume, but Davis then told him to turn it back up.
Officials say Dunn became enraged and he and Davis began arguing. Dunn, who had a concealed weapons permit, pulled a 9 mm handgun from the glove compartment of his car, according to an affidavit, and fired shots into the SUV. Nine bullet holes were found in the car.
Associate medical examiner Stacey Simons testified Monday that the first bullet that hit Davis in the abdomen likely killed him. The bullet went from his lower right abdomen, into his diaphragm, through his liver and hit his aorta, she said.
"I believe it would have been fatal within a matter of minutes," Simons said.
Under cross-examination, Simons said it was unlikely Davis was standing up when he was shot. Dunn's defense attorney, Cory Strolla, had argued in opening statements that Davis had threatened Dunn with a 4-inch knife. Simons said the bullet appeared to have struck something hard, like a car door, before hitting Davis.
Florida Department of Law Enforcement analyst Sukhan Warf said toxicology tests on Davis showed no signs of drugs or alcohol in his body. No gun was found in the SUV.
Another law enforcement department analyst, Maria Pagan, testified earlier in the day about the steps Dunn took before shooting the teen, bolstering prosecutors' contention that he acted with premeditations.
Dunn would have had to remove the gun from its holster, load the chamber with a bullet and then apply six pounds of pressure to fire it, Pagan said.
Dunn fired the gun 10 times, hitting the SUV nine times, and he would have had to pull the trigger every time using more than six pounds of pressure each time, Pagan said.
Pagan answered affirmatively when prosecutor Angela Corey asked, "Does that take a conscious effort of the shooter to have a second-round come out?"
The first witness to testify for the defense was Randy Berry, a friend of Dunn. He said he never knew Dunn to be violent. Berry's wife, Beverly Berry, also testified that she had never seen Dunn with anything but a calm demeanor.
Dunn had been at his son's wedding before the shooting. Dunn's ex-wife, Phyllis Molinaro, and son, Chris Dunn, told jurors that Dunn didn't appear drunk and was in good spirits at the wedding.
The defense attorney also called Davis' father to ask him what he recalled in the days after the shooting.
"I think I said at the time that I was shocked that my son was killed," Ronald Davis said.
At the end of the day, Strolla told the judge he expected to call only one or two more witnesses on Tuesday before wrapping up the defense presentation.