17-year-old boy obsessively listened to the same two lines of one specific track before murdering his entire family

A teenager who is alleged to have killed his entire family was reportedly listening to one song repeatedly before the horrific crime.

Italy has been left in shock after prosecutors claimed a high school student confessed to murdering his family.

A 17-year-old boy is alleged to have attacked his family with a knife at their home in Paderno Dugnano, a town to the north of Milan, on the morning of September 1.

The teenager allegedly stabbed his little brother with a 20cm kitchen knife a total of 10 times, with the 12-year-old 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 called on him to help at which point it is believed the teen tragically launched at him and his mother Daniela.

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 over the deaths of his mom and brother.

The teenager initially told authorities he had killed his father in self defence (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.

However, authorities questioned the teen and hours after taking him in, his story began to unravel, prosecutors say, as it was clear he had no injuries that consisted with that of a struggle.

“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 allegedly told police.

Most disturbingly, the teen also said he had been listening to music by The Beatles days before, repeatedly listening to one line in particular from the song 'The Long and Winding Road', according to local media.

Police found the teenager covered in blood stood outside his home (Family handout)

He told the police that he had listened to the lines ‘Many times I’ve been alone/ and And many times I've cried' on repeat.

The alleged killer also told police: “I realized it a minute later. I understood that it was not by killing them that I would be freed."

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

Police are continuing to investigate the incident.