Wellington Menezes de Oliveira was born on July 13, 1987, and was adopted as a baby by Dicéa Menezes de Oliveira. He was the youngest of five siblings. His biological mother struggled with mental illness and had attempted suicide. Growing up, Wellington was considered a quiet, shy, and introspective boy. He avoided trouble and generally followed rules.

Wellington's adoptive mother, who belonged to the Jehovah's Witnesses faith, died in 2010. Although Wellington participated in the religion with her, he did not fully adhere to its teachings. After his adoptive mother passed away, family members noted that he became even more closed off. They described him as someone who only interacted with people online and had few friends. He spent most of his time in front of a computer, distancing himself from family life.

Wellington faced bullying during his school years, especially while attending the Tasso da Silveira Municipal School from 1999 to 2002. Former classmates recalled that he was often harassed and was given cruel nicknames, such as "Sherman." He experienced physical bullying, including being thrown into a garbage bin and mocked by other students.

In 2001, the terrorist attacks on September 11 had a strong impact on Wellington. Around this time, he expressed feelings of humiliation and pain in letters, mentioning the bullying he endured. On several occasions, he wrote about the struggles he faced, highlighting the mistreatment he suffered at school.

His family was aware of Wellington's mental health issues and had attempted to seek treatment with a psychologist, but these efforts were eventually abandoned. Following his mother’s death, he became more withdrawn. Wellington had shown interest in various religions after disconnecting from the Jehovah's Witnesses, exploring subjects online instead of engaging with people in his life.

On the morning of April 7, 2011, Wellington Menezes de Oliveira entered the Tasso da Silveira Municipal School in Realengo, Rio de Janeiro. He was armed with two revolvers and dressed well. Claiming to be a lecturer, he was allowed inside the school. At around 8:30 AM, he headed to an eighth-grade classroom where he began shooting at the students.

Witnesses reported that he targeted the students specifically, aiming at the girls' heads and the boys' arms and legs. His attack resulted in the deaths of 12 students aged between 13 and 15, and 22 more were injured. The assault was noted to be one of the first significant school shootings in Brazil not linked to gang violence.

As chaos erupted, students and teachers fled the classroom. Local policemen, alerted by an escaping student, responded quickly to the scene. Third Sergeant Márcio Alves managed to shoot Wellington in the leg and stomach. Cornered, Oliveira took his own life by shooting himself in the head.

Following the tragedy, the police started an investigation into how Oliveira obtained his weapons. They learned that he had purchased them through intermediaries and found a letter he left behind, detailing his intention to commit suicide. The investigation unveiled no strong indications of political or religious motivations for his actions, though texts at his home suggested an obsession with violence and Islamic extremist ideas.

In total, twelve children lost their lives that day, and the city mourned deeply, leading to discussions about safety in schools across Brazil. The victims were remembered with memorials and tributes, as the country grappled with the shock of the event.