Guilherme attended elementary school at Antonio Rodrigues de Almeida school. In high school he attended Raul Brazil school from the 10th grade (2016) to the 11th grade (2017). According to the director of the Raul Brasil school, Guilherme attended 10th and 11th grade undisturbedly. He was a quiet student and never bothered teachers. The only time Guilherme's guardians were called at school to talk, was about the bad habit that Guilherme had of be late for classes.
Guilherme usually didn't miss many classes at school, but in the last two months of 2017 his attendance dropped a lot. He attended school for two years, until 2017. In 2018 he dropped school and was planing to get into an adult education program in 2019.
According to reports from students who studied with Guilherme, the boy was constantly bullied. Guilherme was called by several nicknames, among them were: choquito,because of the acne, and "little woman" ("mulherzinha") because of his fine features and long hair. And some students even ask if Guilherme "was in his period", both because he had thinner features and would always become very angry with the provocations (PMS).
Tatiana Taucci, Guilherme's mother, said in an interview that the boy stopped going to school because of the bullying he suffered. But some police officers and investigators says that Guilherme stopped studying to devote himself entirely to planning the massacre.
Benedito Luiz Cardoso, Tatiana's foster father and Guilherme's grandfather said in an interview that Guilherme even talked to him about bullying and his acne. When classes began this year, Guilherme told his grandfather that he didn't want to go to school because he was being bullied a lot, and that he wanted his grandfather to pay him an acne treatment. As he wanted, He didn't attended to school and did the treatment. According to his grandfather, his skin had greatly improved. Guilherme then began to do some temporary work around the city and said that he would attend high school later this year, to finally graduate.
According to reports from some students who studied at Raul Brasil, there was a little confusion involving Guilherme and a boy once. There is few information about this, but what is known is that Guilherme was humiliated by this boy. And supposedly the Inspector Eliana Regina de Oliveira Xavier, 38, had defended the boy who humiliated Guilherme in the confusion, and that made Guilherme deeply angry. Apparently this incident marked him forever so based on this story, there are great chances that Eliana's death had already been premeditated by Guilherme long ago as a form of revenge for it.
Guilherme is described by some students as a quiet, introverted boy who always went unnoticed. Many of the students (even those who had studied with him) didn't even recognised Guilherme when they saw him committing the massacre.
According to Vitor Grilo (the third suspect of them massacre) Guilherme was not bullied. In his view, it was Guilherme who bullied and mocked others, especially the "funkeiros" (people who likes or plays the music styles of funk carioca, usually this people are poor and lives in shanty towns) of the school and the “noiados” (people who use drugs). Vitor, studied with Guilherme in 2016, and says that Guilherme always said that one day he would repeat the Columbine massacre.
A school employee who prefered not to identify herself reported in an interview she met Guilherme at school, and he had a special affection for her. She also said that he had several psychological problems, but didn't go into details.
Reliable sources (?) Says that Guilherme had the habit of making an gun symbol with his hands and pretending to shoot people during the recess.
Again: All the credits goes to MentosD3ploy.