Gunman': Claudio Giardiello was described as 'very unusual' and 'over the top' by his former lawyer . A gunman has killed four people - including a judge and a witness - after going on a rampage at a Milan court where he was due to appear today accused of fraudulent bankruptcy. The defendant, Claudio Giardiello, 46, is said to have first killed his lawyer Lorenzo Alberto Claris Appiani, 37, and his co-defendant before shooting dead judge Fernando Ciampi  in an act of revenge 'against those that ruined me'. Prosecutors said the attack was carried out with 'cold premeditation'. A fourth victim, understood to have been a witness, had no visible injuries and is thought to have died of a heart attack. Several other people suffered serious injuries in the attack, including Giardiello's former colleagues and accountant. After his killing spree, the gunman managed to evade police and fled the courthouse on his motorbike, reaching the town of Vimercate 15 miles from Milan before being arrested. Giardiello likely used a false ID pass to enter the court through a side door reserved for judges and lawyers, who are not obliged to have their belongings scanned by a metal detector, Milan public prosecutor Edmondo Bruto Liberati said. Prime Minister Matteo Renzi said the attack 'a moment of great pain, of sadness' adding that it was 'unthinkable someone should be able to enter a court with a weapon.' He promised 'the government will shed the utmost light on the event' and described the police who had chased down and arrested the man as heroic. The gunman's attack began when he fired four or five rounds from multiple weapons at 11am. Witnesses reported barricading themselves inside their offices and taking cover under their desks as police hunted for the gunman. After texting loved ones that they were OK, employees and lawyers were eventually allowed to trickle out of the tribunal, women first, followed by the men who had their court ID cards checked. Gunman: Claudio Giardiello (centre) - the man who killed four people after opening fire on a Milan courthouse - is escorted by Italian police officers in Vimercate barracks near the city . Casualty: Rescuers and police help a seriously injured man out of the Justice Palace in Milan this morning . Several others suffered serious injuries in the attack, including Giardiello's ex-colleagues and accountant . Hundreds of people were eventually evacuated from the building as police hunted the gunman. 'There was a lot of panic at the beginning when people came running towards us saying there was a person with a pistol who had been shooting,' said lawyer Mirko Ricetti, who said he locked himself in a first-floor courtroom after hearing a shot. Police said Giardiello fired 13 rounds in total, beginning his rampage by mortally wounding his co-accused, Giorgio Erba, and killing his lawyer Mr Appiani. Another of his co-accused, Davide Limongelli, was injured in the gunfire. The armed assailant then allegedly sought out judge Ciampi, shooting and wounding another man on the stairs on the way to the floor below. He allegedly entered the judge's private office, letting off two shots that killed him instantly. Mr Bruti Liberati said it was not clear whether there was any relationship between the gunman and the judge. After his killing spree, the gunman managed to evade police and fled the courthouse on his motorbike, reaching the town of Vimercate 15 miles from Milan before being arrested . Giardiello was caught on video surveillance cameras fleeing the court and police traced him via his numberplate. Interior Minister Angelino Alfano later issued an update saying the suspect was arrested in a village 15 miles from central Milan away after fleeing the scene on a motorcycle. He subsequently tweeted: 'Caught in Vimercate the alleged murderess of Milan'. He told a press conference it appeared the man 'was ready to kill others in Vimercate,' following reports Giardiello had been heading towards another co-defendant, who was not present in court. Giardello, who reportedly had a string of failed businesses, allegedly told police: 'I wanted to take revenge on those that ruined me', according to Italian news agency ANSA. He owned 55 per cent of a real estate company which went under in 2008, media reports said. An ambulance with escort was seen leaving the Vimercate police station, but it was not immediately clear if the gunman was inside. Valerio Maraniello, who once acted as a lawyer for the shooter, told AFP his ex-client was 'an aggressive person, a little paranoid.' 'He was always convinced people were trying to cheat him. He never listened to advice,' he said, adding that he was 'not completely surprised' by the deadly attack. Hundreds of people were evacuated from the Palace of Justice building as police searched for the gunman . A plain clothes police officer helps to evacuate people from the tribunal building in Milan this morning . Leaders across the political sphere expressed shock that a gunman had managed to get into the court building. 'The fact that we're not talking about an organisation which surveyed the place first makes it even more perturbing,' said the head of the Lombardy region, Roberto Maroni. Alfano - in Milan for a meeting on public order and safety ahead of the 2015 Milan expo which opens in May - promised to investigate what he described as 'serious errors' in security. 'If this is the level of security in Expo Milan imagine what potential terrorists can think of doing,' said Matteo Salvini, head of the anti-immigration Northern League party. Judge Gherardo Colombo told journalists outside the court that he had known the murdered judge well. 'It's absurd that one can die like that, while you're doing your job,' he said, suggesting 'an anti-judiciary climate' may be to blame. The shooting immediately raised questions about how the man gained entrance to the Fascist-era courthouse with a weapon, given that visitors must pass through metal detectors. Heavily armed: Police snipers arrive at Milan's Palace of Justice this morning following the shooting . Security: Police cars surround Milan's Palace of Justice building this morning after a man named locally as Claudio Giardiello opened fire. Four people are thought to have died . The courthouse has metal detectors at the four main entrances, but lawyers and courthouse employees with official IDs are regularly waved through without the additional security screen and accredited employees can drive into the internal garage. Lawyers Mirko and Davide Pupo noted that the metal detector from the lawyers' entrance had been removed several months ago. Employees who emerged after the shooting suggested that the gunman could easily have gained entrance without passing through the metal detector by entering with his lawyer, though other lawyers said their clients are routinely told to go in via the public entrance. Deputy interior minister Filippo Bubbico said an investigation would determine who was to blame for any security lapse, given also that the gunman was not stopped as he moved from one floor to the next to continue the spree, and then was able to flee unimpeded. The Palace of Justice is in the historic centre of Milan, only a few streets away from the city's cathedral and shopping district.
Suspect Claudio Giardiello wanted revenge 'against those that ruined me'
Judge Fernando Ciampi among targets killed with 'cold premeditation'
Gunman 'used a fake ID to enter court through door reserved for lawyers'
Arrested 15 miles away 'while seeking out another victim not in court'