Luigi Padovese, the pope’s apostolic vicar in Anatolia, was attacked outside his home in the Mediterranean port of Iskenderun.
Mehmet Celalettin Lekesiz, the governor for the province of Hatay, said police immediately caught the killer.
He said the man, identified only as Murat A., was Bishop Padovese’s driver for the last four and a half years and was mentally unstable.
“The initial investigation shows that the incident is not politically motivated,” Mr Lekesiz said.
“We have learned that the suspect had psychological problems and was receiving treatment.”
Bishop Padovese, the equivalent of the bishop for the Anatolia region, was due to leave for Cyprus tomorrow to meet the pope, who is visiting the island, and fellow bishops from around the region for preparations before the church’s synod of bishops on the Middle East in October.
A Vatican spokesman said the death showed the “difficult conditions” that the Catholic community in the region lives in.
The killing is the latest in a string of attacks in recent years on Christians in Turkey, where Christians make up less than 1% of the 70 million population.
In 2007, a Catholic priest in the western city of Izmir, Adriano Franchini, was stabbed and wounded by a 19-year-old man after Sunday Mass.
The same year, a group of men entered a Bible-publishing house in the central Anatolian city of Malatya and killed three Christians.
The killings – in which the victims were tied up and had their throats slit – drew international condemnation and added to Western concerns about whether Turkey can protect its religious minorities.
In 2006, amid widespread anger in Islamic countries over the publication in European newspapers of caricatures of Islam’s Prophet Muhammad, a 16-year-old boy shot dead a Catholic priest, Father Andrea Santoro, as he prayed in his church in the Black Sea city of Trabzon. The boy was convicted of murder and sentenced to 18 years in prison.