Around 70 people sat down for Sunday lunch in the packed "Osteria dei Amis" in Gugnano near Milan with reporters and some politicians joining villagers in a show of support for 67-year-old Mario Cattaneo.
The chef-owner killed a burglar with a single shot from his hunting rifle early on Friday after three intruders broke into the restaurant while he and other members of his family were sleeping in the flat upstairs.
A local magistrate has placed him under formal investigation on suspicion of voluntary manslaughter, a charge which carries a minimum prison term of 21 years.
The move has sparked outrage among some Italian politicians and calls for a change to the law covering so-called legitimate defence cases.
Cattaneo told reporters outside his restaurant that his gun had gone off during a scuffle with one of the burglars.
"It went off when I fell to the ground. One of them was trying to grab the gun off me and he dragged me along for several metres," he said.
"It was dark and I didn't see what happened. I only found out someone had died when I was in hospital. I'm really sorry that someone has lost their life."
In support of his story, the chef-owner showed reporters bruises on his arms he said had been incurred in the scuffle.
The dead man has been identified as a 33-year-old Romanian national who lived locally. He had been shot in the back and his body was found around 100 metres (yards) from the property.
Opposition parties have attempted to capitalise on the case to highlight what they see as out-of-control crime.
Maurizio Gasparri, a close ally of former billionaire prime minister Silvio Berlusconi, is fund-raising for the restaurateur's legal bills.
And Northern League leader Matteo Salvini has called for changes to the law so that self-defence can automatically be invoked in such cases.
As things stand, accused parties usually have to show they had reasonable grounds to fear for their own life to avoid a murder charge.
But some judges have also allowed a "legitimate defence" argument based on a pattern of being regularly targeted by criminals.