A shooter opened fire on his apartment building’s residents’ association in a bar in a northern district of Rome on Sunday following an alleged dispute over housing, Italian media reported, sending shockwaves through Italy where such incidents are almost unheard of.

Italian prime minister Giorgia Meloni said in a Facebook post later on Sunday that one of the three victims was a friend.

Rome Mayor Roberto Gualtieri called an emergency security meeting on Monday after what he called a “grave episode of violence.” In a tweet, he confirmed three people were killed in the shooting in the Fidene neighbourhood.

“The shooting occured in an enclosed outdoor seating area of the bar, called “Il Posto Giusto,” or “The Right Place”, he said.

Police had not issued a statement on Monday morning, but Meloni said the suspect had been arrested.

The suspected shooter, 57-year-old Claudio Campi, allegedly used a Glock pistol stolen from a firing range.

In a post on his blog in November, he wrote of his conflictual relationship with the people managing the building, who he accused of trying to force him out of his lodgings.

Italy’s La Repubblica newspaper quoted witness Luciana Ciorba, vice president of the residents’ association, as saying the man entered the bar shouting “I’ll kill you all,” before opening fire.

Witnesses managed to disarm him until Carabinieri police arrived.

Speaking in a video interview, Ciorba said the man was known to board members and had been previously reported to authorities for making threats against local residents, AP reported.

Of the three women who died of their wounds, one was Nicoletta Golisano, 50, mother of a 10-year-old boy, who was attending the meeting as treasurer.

Meloni revealed on Facebook they were friends and paid tribute to “a protective mother, a sincere and discreet friend, who was also a strong and fragile woman”.

In addition to Golisano, Sabrina Sperandio, 71, and Elisabetta Silenzi, 55, were also killed.

The two served respectively as councillor and accounting secretary of the residents’ association, according to La Repubblica.

An 80-year-old and 50-year-old woman were also taken to hospital with serious skull injuries, the outlet reported.

Though Italy has a higher rate of gun homicides compared to most other G8 countries, mass shootings such as those regularly seen in the US are extremely rare.

According to the latest available data from the United Nations Office on Drugs and Crime, there were 0.8 murders committed by firearms in Italy per 100,000 members of the population. That’s a long way off the USA’s figure of 3.8, but still the second highest of the G8 countries.