As many as 11 students were killed and another 18 wounded Thursday when a gunman went on a shooting rampage inside a Brazilian school.
The shooter marched into classes, blasting kids as young as 12 in the face and chest before finally turning his weapons on himself as police closed in.
Brazil's President Dilma Rousseff said she was "shocked and disturbed" by the massacre that claimed the lives of one boy and ten girls at the Tasso da Silveira school in Realengo, western Rio de Janiero.
Authorities identified the killer as 24-year-old Wellington Menezes de Oliveira, an ex-student, according to Brazilian media reports.
Dressed smartly and wearing a backpack, he headed to his former school at around 8:30am local time, O Globo wrote, walking through two sets of metal gates before announcing to staff he was there to give a lecture.
Menezes de Oliveira was armed with two loaded revolvers, the Rio-based newspaper said.
The shooting began in a Portuguese language class where teachers said he silently pulled out a pistol and opened fire on the 40 pupils as they sat at their desks.
As shots rang out throughout the building, staff herded petrified children into a top-floor auditorium before barricading the door with tables, chairs and cabinets.
Realizing the building was surrounded by police officers, Menezes de Oliveira then made a dash for the upper floors, making it as far as the third floor where he was shot in the leg by a pursuing cop, according to O Globo. The newspaper claimed the shooter then killed himself as the officer approached.
Witnesses told Brazilian television the gunman fired at least 50 shots at students and police during the 20-minute rampage which began just after the morning bell ushered in the start of the school day.
A makeshift hospital was rigged-up on a nearby soccer field to give victims first aid before the most serious cases were taken to the hospital. As many as 18 children were hospitalized, according to various reports, four in critical condition.
Anguished parents, meanwhile, gathered outside the school's gates, desperate for news of their kids. But police moved people on as medics treated injured students and detectives began their investigation, TV GloboNews said.
Eluzia, a woman who lives opposite the school, told AFP that her 10-year-old son escaped the attack.
"He looked out the window when he heard the shots, and when he didn't see anything he started running for the door. Thank God he's fine," the woman said. "I saw many more people running, people who had been shot. It was horrible," she added.
The killer is believed to have penned a rambling suicide note but its contents have not been disclosed. An unconfirmed report by CNN, citing a local official, suggested the letter mentioned the fact the gunman was HIV positive.
Another Brazilian newspaper, O Dia, claimed the note referred to "impure people." It said investigators were considering whether this was a reference to women, given that the majority of the victims were girls. The letter also included references to Islam and terrorist practices but was largely incomprehensible, the paper said.
Amid the chaos and bloodshed Thursday, there was some confusion over the eventual death toll, with an initial figure of 13 revised down by most media outlets to 11. AFP put the toll at 10, quoting Rio de Janeiro state's health department chief Sergio Cortes.
President Rousseff made a brief TV appearance, saying she was "shocked and disturbed" at the shooting. "Innocent children lost their lives and their future," she added.
Education minister Fernando Haddad described the attack as "an unprecedented tragedy in Brazil," AFP said.
Read more: GloboNews