A campus shooting in Rio de Janeiro on Thursday morning killed 11 people and injured at least 22 others, the city's health chief, Sergio Cortes said.

11 children were killed and 22 were injured in a deadly school shooting incident in Rio de Janeiro on Thursday.

In one of the worst cases of its kind in Brazil's history, 23- year-old Wellington Menezes de Oliveira entered a public school in Rio's western region, shot dead at least 10 students and then committed suicide.

According to local police, the 10 victims include nine teenage girls and one teenage boy, all aged between 12 and 14. And at least 18 injured teens are now receiving treatment at the local Albert Schweitzer Hospital.

Police said the shooter was a graduate of the school. A city education official said the gunman came to the school one year ago, indicating the shooting was a premeditated crime.

Menezes' motives remained unclear. According to a police spokesman, the shooter left a note, in which he stated that he was HIV-positive and believed "kids are impure."

He entered the Tasso da Silveira school in the neighborhood of Realengo around 8 a.m. local time, saying he would give a lecture to the 8th graders. Then, he reportedly entered the classroom and started shooting randomly. One of the students managed to escape and called the police.

Menezes tried to escape, but he was intercepted by a police officer, who ordered him to drop his two revolvers.

As the killer refused to do so, the officer shot Menezes in the leg. After being injured, according to the police, Menezes shot himself dead.

Brazil's President Dilma Rousseff, who learned the news at a public meeting in Brasilia, said: "This sort of crime did not use to happen in Brazil. I think that everyone here, men and women, is joined in repudiation to this act of violence against defenseless children."