Panama's Electoral Tribunal has lifted former President Ricardo Martinelli's immunity from prosecution, clearing the way for authorities to investigate him for alleged corruption.

The lifting of Martinelli's immunity as a member of the Central American parliament had been requested by Panama's Supreme Court and frees it to proceed with his prosecution. The decision was made Tuesday and announced the following day.

The billionaire supermarket magnate faces accusations that he inflated contracts worth $45 million to purchase dehydrated food for a government social program.

Martinelli has denied the charges and says he is the target of persecution by his successor, Juan Carlos Varela. He has left the country and his whereabouts are unknown.

Martinelli governed Panama from 2009-2014, a period of high economic growth but also of corruption, his critics say.

A real estate developer on trial for fraudulent bankruptcy fired 13 shots inside the Milan Tribunal on Thursday, killing his lawyer, a co-defendant and a judge, eluding court security before being captured 25 kilometers away.

The shooting raised concerns about security at Italy's courthouses, where much of the surveillance has been outsourced to private contractors, and about Italy's ability to protect visitors during the Milan Expo 2015 world's fair, which opens May 1 and is expected to attract 20 million visitors over six months.

Premier Matteo Renzi pledged a robust investigation into how the gunman, identified as Claudio Giardiello, managed to bring a pistol into the monumental Fascist-era tribunal, where defendants and other visitors are required to pass through metal detectors, but accredited court officials, including lawyers, are not.

"Our commitment is that this never happens again, and that those responsible pay," Renzi said.

The chief federal prosecutor in Milan, Edmondo Bruti Liberati, told reporters it appeared Giardiello may have used a fake document to enter through the only pedestrian entrance not equipped with a metal detector and intended only for use by accredited court officials. He said the metal detectors at the other entrances were in good working order.

Bruti Liberati praised law enforcement, who apprehended Giardiello at a shopping center more than an hour after the shooting. They had identified the license plate on his motor bike with video surveillance cameras and tracked his arrival in Vimercate, some 25 kilometers (15 miles) from the scene in the heart of Milan.

Prosecutors said Giardiello, 57, was still armed with a loaded pistol and intended to kill another business partner whom he blamed for a failed real estate venture.