A 13-year-old boy killed his police officer parents, his grandmother and his great-aunt then spent a full day at school before returning home to take his own life.

Marcelo Pesseghini was found dead with the bodies of his relatives at the family’s home in Sao Paulo, Brazil.

His father, police sergeant Luiz Pesseghini, 40, was discovered in bed while mother, Andreia, 30, who served in the military police, was found on her knees in the bedroom.

His grandmother, Benedita de Oliveira Bovo, 65, and great-aunt Marie Das, 55, were also dead in bed in a different section of the house.

The teenager died from a shot to the left temple, his father’s police-issue service revolver found nearby, Sao Paulo police commander Benedito Roberto Meira said.

A second gun, a .32 calibre revolver, was found inside the backpack the teenager had brought to school on Monday, Meira added, saying “there was no sign that someone broke into the house.”

Police believe the schoolboy shot each victim in the head with a .40 caliber pistol early Monday morning before catching a lift into school with a friend.

Itagiba Franco, of the Sao Paulo Civilian Police’s homicide department, said Pesseghini had told a friend he wanted to kill his parents and become a hitman.

“He always told me he wanted to become a hired killer,” police quoted the friend as saying.

“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.”

Commander Meira ruled out “an act of revenge by a criminal group” against the teenager’s father and mother.

Read more: Mirror News