JACKSONVILLE, Fla. — After four days of deliberation, the jury in the racially tinged trial of Michael Dunn, a Florida man who set off another firestorm over the state’s self-defense laws when he shot a teenager to death in a parking lot during a dispute over loud music, said it could not agree on whether Mr. Dunn had acted to protect himself or was guilty of murder.

The jurors did find Mr. Dunn guilty of three counts of second-degree attempted murder for getting out of his car and firing several times at the Dodge Durango sport utility vehicle in which Jordan Davis, 17, was killed. Three other teenagers, the subjects of the attempted murder charges, were in the car but were not struck. Mr. Dunn continued to fire at the vehicle even as it pulled away. On the attempted murder convictions, he could be sentenced to 60 years in prison.

Judge Russell L. Healey of Duval County declared a mistrial on the count of first-degree murder, which applied only in the death of Mr. Davis. The jury also failed to reach agreement on lesser charges that are automatically included in jury instructions. Those were second- and third-degree murder and manslaughter.

The state attorney for Jacksonville, Angela Corey, said immediately after the verdict that she planned to retry Mr. Dunn on first-degree murder. Ms. Corey said she hoped jurors would explain why they could not agree on that charge, which could help her team in the new trial.