MIAMI — The South Florida musician who was killed by the police early Sunday after his car broke down near a highway exit ramp was armed with a handgun he had bought three days earlier, the Palm Beach Gardens police chief said Tuesday.

The musician, Corey Jones, 31, was shot by a plainclothes officer who had been on the job for six months, Chief Stephen J. Stepp said. Mr. Jones’s handgun was recovered on the ground outside his car; the new box it came in was inside, the chief said.

In a brief news conference Tuesday night, Chief Stepp addressed the swelling questions about how a respected church drummer and housing inspector wound up dead in the middle of the night off Interstate 95, a half-hour from his home. The case, another focused on the shooting of a black man by a police officer, had begun to gain attention on social media, and the department was sharply criticized by a county police union official for not coming forward with facts sooner.

The investigation into the shooting is being conducted by the Palm Beach County sheriff’s office, a different agency, so the chief stressed that his knowledge of the shooting was limited. He offered his condolences to Mr. Jones’s family and said the department had tried to meet with them.