Four people were killed on Thursday during a televised shootout on a traffic-choked roadway outside Miami after an attempt to rob a jewelry store ended in the hijacking of a UPS truck, the kidnapping of its driver and a police chase across two densely populated South Florida counties.

The exchange of gunfire in Miramar, Fla., killed the UPS driver as well as the two carjackers who kidnapped him, according to George Piro, the special agent in charge of the F.B.I.’s Miami field office. He described the fourth person killed as a bystander, but on Friday he publicly released only the names of the two people who he said were responsible for the robbery and abduction.

Video of the shootout, which pitted more than a dozen law enforcement officers against the carjackers, who fired from inside the stolen truck, was broadcast by television networks in South Florida and circulated widely online. The video shows occupants of other vehicles scrambling as gunfire erupts around them during the afternoon rush in Broward County.

It was not immediately clear if the UPS driver and the bystander, who were identified by family members and their employers Friday as Frank Ordoñez and Rick Cutshaw, respectively, were killed by the carjackers or the police.