An ambulance crew was then attacked by an angry crowd of onlookers on their arrival at the scene in the San Basilio suburb, leaving one ambulance driver with a fractured shoulder.
Moreno Coppi was shot in the head by 32-year-old Maurizio Alletto after their cars collided, the paper said. Coppi had been driving with his father, Luciano, who tried to intervene.
A 25-year-old man was also taken to hospital with stab wounds.
Rome’s new mayor Ignazio Marino released a statement saying “we cannot accept such serious incidents to occur in our city, especially when men and women, who provide assistance to those in need, are brutally attacked.”
Nicola Zingaretti, the president of the Lazio region, has called for an investigation into the incident.
Livio De Angelis, the director of the 188 emergency services, said he was outraged by the attack on ambulance staff.
"I can’t understand how anyone could hate those trying to save a life,” he said.
La Stampa described San Basilio, in Rome's eastern suburbs, as an area of "drug dealers, convicts and decent people, who can only afford to live there for a roof over their heads."