"They were jumping on him when he was lying helpless on the ground" says key witness in killing of Willy Monteiro Duarte.

An autopsy carried out on the body of Willy Monteiro Duarte, who was beaten to death by a gang in a town near Rome, has revealed that he died as a result of 'polytrauma' - multiple traumatic injuries - to his chest, abdomen and neck, which led to cardiac arrest.

These are the preliminary results of the autopsy, however further clinical tests are required to ascertain which blow was fatal for the 21-year-old Cape Verdian-Italian man who died in Colleferro in the early hours of 6 September.

The results of these further investigations could reveal details that could alter the current charge - involuntary manslaughter - facing the four arrested in relation to Willy's death - to the more serious charge of voluntary manslaughter, reports Italian newspaper La Repubblica.

• Italy mourns Willy, beaten to death by gang

Emanuele Cenciarelli, a key witness of the savage beating which resulted in the death of his friend Willy said: "They were jumping on him when he was lying helpless on the ground," reports Italian newspaper Corriere della Sera.

Three of the four arrested, currently in Rome's Rebibbia prison, have been named as brothers and mixed martial arts practitioners Gabriele and Marco Bianchi, aged 26 and 24; and Mario Pincarelli, 22.

The fourth, Francesco Belleggia, 23, has left Rebibbia to go under house arrest after an investigating judge recognised his "more nuanced role" in the attack, reports Corriere della Sera.

On 9 September magistrates reconstructed a scene of "unmotivated and unprecedented" violence against a young man who "had nothing to do with" the fight that was triggered by a trivial matter.

• Italy: Bianchi brothers deny killing Willy Monteiro Duarte

Last night hundreds of people attended a candle-lit procession, demanding "Justice for Willy" in Duarte's hometown of Paliano, near Colleferro, including the Cape Verde ambassador, with many wearing white t-shirts that read "Ciao Willy".

Duarte's funeral is likely to take place at the sports field in Palliano on 12 September, reports La Repubblica.

The killing has caused outrage in Italy, with a torrent of rage directed at those accused of Willy's death, particularly the Bianchi brothers who claim: "We never touched him."

Photo TgSky24