The shooting panicked tourists and locals in the square on a rare sunny day at the end of a four-day holiday weekend.
A video surveillance camera on the Parliament building caught the attacker on film just before and during the shooting, Italian news reports said. In the film, the shooter is seen walking at a steady pace along a narrow street that leads from near Parliament's lower house to the edge of Colonna Square, where police officers appear to have stopped him to ask where he was going. Shortly after that, the man begins firing, the surveillance camera showed, according to the reports.
Alfano said Preiti wanted to kill himself after the shooting, but ran out of bullets. He said six shots were fired in all. Laviani said the assailant had obtained his weapons on the black market.
reported that Preiti had taken a train to Rome from Calabria on Saturday, and that police found his car parked at a southern train station.
The interior minister said security was immediately stepped up near key venues in the Italian capital, but added authorities were not worried about possible related attacks.
"Our initial investigation indicates the incident is due to an isolated gesture, although further investigations are being carried out," he said.
The ministers were kept briefly inside for security reasons until it was clear there was no immediate danger.
Preiti's uncle, interviewed by
, said the alleged gunman had moved back to his parents' home in Calabria because he could no longer find work as a bricklayer. "He was a great worker. He could build a house from top to bottom," the uncle, Domenco Preiti, said.
The shooting revived ugly memories of the 1970s and 1980s in Italy, when domestic terrorism plagued the country during a time of high political tension between right-wing and left-wing blocs.