A 13-year-old Brazilian boy killed his parents, grandmother and great aunt before spending a full day at school and then taking his own life.

Marcelo Pesseghini is thought to have killed his military officer parents in their bedroom using a police issue .40 calibre pistol. The boy’s father, 40-year-old Luiz, was found dead in his bed, while his 30-year-old mother Andreia was discovered on her knees on the bedroom floor.

Marcelo Pesseghini’s grandmother, 65-year-old Benedita de Oliveira Bovo, and his great aunt, 55-year-old Bernadete Oliveira da Silva, were also found dead in their beds, but in a separate part of the same building. All four victims had suffered gunshot wounds to the head.

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Police believe that after killing his family, Marcelo Pesseghini caught a lift to school with a friend and spent a full day in lessons.

CCTV footage captured him calmly walking home from school later in the day, but he was subsequently found dead from a gunshot wound to the temple. His father’s revolver was found nearby and a .32 gun found in his school backpack.

It is thought Marcelo Pesseghini killed his family after being inspired by a mass murder that took place in Amityville, New York in 1974.

In that case a man named Ronald DeFeo Jr. killed his parents, two brothers and two sisters as they slept in their beds. The case was the inspiration for a book and film called The Amityville Horror, in which investigators examine evidence that the victims continue to haunt the property in which they were killed.

Marcelo Pesseghini uploaded a famous photo which some claim shows the ghost of one of the victims – an image widely known as the Amityville Ghost Boy – to his Facebook page shortly before Christmas last year.

At a press conference Itagiba Franco of Sao Paolo’s civilian police force said: “Everything seems to indicate that Marcelo killed his parents and relatives”.

Reading from a statement the friend of Pesseghini’s had made, Mr Franco added: “He always told me he wanted to become a hired killer. He had a plan to kill his parents during the night, so that no one would notice and escape in the parents' car and live in an abandoned place”.