Police believe Marcelo Pesseghini shot each victim in the head with a .40 caliber pistol early Monday morning at the home in Sao Paulo, Brazil, before catching a lift into school with a friend.
The father, Luiz Pesseghini, 40, a police sergeant with 19 years service was found in bed. The mother, Andreia Pesseghini, 30, who had served in the military police for 16 years was found on her knees in the bedroom. (Marcelo and his parents pictured above)
The grandmother, Benedita de Oliveira Bovo, 65, and great-aunt Bernadete Oliveira da Silva, 55, who lived in a different section of the house were both killed in bed.The teenager was found dead from a gunshot to the left temple and his father's police-issue service revolver was found nearby.
A second gun, a .32 caliber revolver, was found inside the backpack the teenager took to school.
The teenager appears to have been inspired by the infamous Amityville killings of 1974 when a man killed his parents, two bothers and two sisters at their home in Amityville, Long Island, New York. All were found dead in their beds.
|CCTV footage from a security camera shows Marcelo Pesseghini casually walking to school in the early hours of Monday morning|
CCTV footage taken from a security camera close to the property in the Brasilândia district in the northern part of São Paulo appears to show him casually walking back home after school.
'Everything seems to indicate that Marcelo (Pesseghini) killed his parents and relatives,' Itagiba Franco, of the Sao Paulo Civilian Police's homicide department, told a press conference.
Franco said Pesseghini had told a friend he wanted to kill his parents and become a hitman.
|Marcelo and his dad|
Sao Paulo police commander Benedito Roberto Meira said there was no sign that someone had broken into the house and ruled out 'an act of revenge by a criminal group' against the teenager's father and mother.
Worryingly the teenager appears to have been inspired by the infamous Amityville killings with the crimes bearing chilling similarities to the 1974 murders.
In the early hours of November 13, 1974, Ronald DeFeo Jr killed his parents-Ronald and Louise and four siblings. All were found dead in their beds.
The Amityville killings later sparked rumours of the supernatural after it was claimed that the house where they took place was haunted.
A famous picture known as the Amityville Ghost Boy which emerged in 1976 purports to show the ghost of the youngest victim of the massacre.
In December last year Marcelo Pesseghini posted the Ghost Boy picture, on his Facebook page.