Father made one final heroic act before being stabbed to death by son who killed mom and brother

A father made a devastating final heroic act before he, his wife and son were allegedly murdered by their eldest son.

In the early hours of Sunday morning (September 1) in Paderno Dugnano, a town to the north of Milan, Italy, a 17-year-old boy is believed to have crept into his little brother's room armed with a knife.

The 12-year-old was then stabbed a total of 10 times, letting out a loud scream that woke his parents in the process.

Oblivious that their eldest son, who was already in the room when they arrived, was the accused killer, dad Fabio Chiarioni heroically called on him to help - at which point it is believed the teen tragically launched an attack on them.

The son then dialled the emergency services for help, AP reports, with him initially claiming to have killed only the father in self-defense and blaming him on the deaths of his mom and brother.

The Italian family are all believed to have died at the hands of one of their own family members (Family Handout)

When police arrived at the scene the boy was stood outside in front of his home covered in blood, wearing just his underwear while gripping a knife - which he dropped the moment cops arrived, officials reported.

When officers began questioning the teen, he continued his claim that his dad was the attacker, and told them how he witnessed Chiarioni stab his mom and his little brother before then turning on him.

According to local media, following hours of questioning it became apparent that his alibi began to unravel and he had no injuries that consist with those of a struggle.

Speaking to investigators, the teen said: “There is no real reason why I killed them. I felt like a foreign body in my family. Oppressed. I thought that by killing them all I would free myself from this discomfort."

He went on to explain how he felt 'discomfort' within his family and it all came to a head on his dad Chiarioni's 51st birthday.

Heroically, the dad yelled at his eldest son to help before becoming a victim himself (Family Handout)

“I realized it a minute later. I understood that it was not by killing them that I would be freed,” he told cops.

Speaking about the family, the mayor of the town Anna Varisco said: “They were a normal, serene family, not followed by social services and described by everyone as not having problems."

While the dad of a school classmate of the alleged teen killer added: “They were a fantastic, happy family. It’s impossible, I don't know what could have happened."

Meanwhile, a juvenile prosecutor in Milan, Sabrina Ditaranto said during a press conference on Sunday: “The boy understood that he had done something irreversible, he expressed his own discomfort, not related to the family."

The investigation continues.