JACKSONVILLE, Fla. (AP) — A 47-year-old software developer was convicted Saturday of attempted murder for shooting into a carful of teenagers after an argument over what he called their "thug music," but jurors couldn't agree on the most serious charge of first-degree murder.

After more than 30 hours of jury deliberations over four days, a mistrial was declared on the murder charge that Michael Dunn faced in the fatal shooting of one of the black teens. The 12 jurors found him guilty of three counts of attempted second-degree murder and a count of firing into an occupied car.

Dunn was charged with fatally shooting 17-year-old Jordan Davis, of Marietta, Ga., in 2012 after the argument over loud music coming from the parked SUV occupied by Davis and three friends outside a Jacksonville convenience store. Dunn, who is white, had described the music to his fiancee as "thug music."

Dunn showed no emotion as the verdicts were read. A sentencing date will be set at a hearing next month. Each attempted second-degree murder charge carries a maximum sentence of 30 years in prison, while the fourth charge carries a maximum of 15.

Davis' parents each left the courtroom in tears, and afterward his mother, Lucia McBath, expressed gratitude for the verdict. Sunday would have been the teen's 19th birthday.

"We are so grateful for the charges that have been brought against him," said McBath said of Dunn. "We are so grateful for the truth. We are so grateful that the jurors were able to understand the common sense of it all."

On Dunn's potentially lengthy sentence, Davis' father, Ron Davis, said: "He's going to learn that he must be remorseful for the killing of my son, that it was not just another day at the office."

State Attorney Angela Corey said her office planned to retry Dunn on a first-degree murder charge, and she hoped jurors would come forward and tell prosecutors where they questioned their case. Jurors declined to talk to the media.

Earlier in the day, the panel said in a note to Judge Russell L. Healey that they were having trouble reaching agreement on the murder charge. He asked them to continue their work, and they went back to the deliberation room for two more hours.

"I've never seen a case where deliberations have gone on for this length of time ..." Healey said after the verdict. "They've embraced their civic duty and they are to be commended for that."

Dunn claimed he acted in self-defense, testifying he thought he saw a firearm pointed at him from the SUV as Davis yelled insults at him and the argument escalated. No weapon was found in the SUV.

Dunn told jurors he feared for his life, perceiving "this was a clear and present danger." Dunn, who has a concealed weapons permit, fired 10 shots, hitting the vehicle nine times.

Prosecutors contended that Dunn opened fire because he felt disrespected by Davis. The teen made his friend turn the music back up after they initially turned it down at Dunn's request. Dunn was parked in the spot next to the SUV outside the convenience store.

"That defendant didn't shoot into a carful of kids to save his life. He shot into it to save his pride," Assistant State Attorney John Guy told the jury earlier in the week. "Jordan Davis didn't have a weapon, he had a big mouth."

The trial was the latest Florida case to raise questions about self-defense and race, coming six months after George Zimmerman was acquitted in the shooting of 17-year-old Trayvon Martin in Sanford, about 125 miles south of Jacksonville. The Dunn trial was prosecuted by the same State Attorney's Office that handled the Zimmerman case.

Dunn's attorney, Cory Strolla, told reporters before the verdict that he believed there was political pressure on the prosecutors and an excess of media attention because of Zimmerman's acquittal.

"I believe there is a lot vested in this case, politically," Strolla said. "The case, on the heels of not guilty in George Zimmerman, just escalated that political pressure."

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Associated Press writer Jennifer Kay in Miami contributed to this report.