Police and government officials in the state of Santa Catarina said the man had also wounded four victims at the private preschool, known as the Good Shepherd Center, in the morning attack in the city of Blumenau.
He then handed himself in at a state police station and was arrested, police said in a statement.
President Luiz Inacio Lula da Silva condemned the attack as a “monstrosity.”
“There is no greater pain than a family that loses children or grandchildren, even more so when it is in an act of violence against innocent and defenceless children,” he wrote on Twitter.
“My thoughts and prayers are with the victims’ families.”
Images from the scene on Brazilian news site G1 showed emergency workers and police outside the preschool, as dozens of people waited behind a security cordon.
An officer asked the crowd to remain calm, saying only parents were being allowed inside.
A state government source confirmed to AFP the four victims were children.
The three boys and one girl were between five and seven years old, G1 reported.
The weapon used resembled a hatchet, Brazilian media reports said.
Three-day mourning
Santa Catarina Governor Jorginho Mello declared three days of mourning in the state for the “terrible” attack.
Violence in schools has been increasing in Brazil in recent years.
Last week, a 13-year-old boy killed a teacher in a knife attack at a school in Sao Paulo.
In November, a 16-year-old shooter killed four people and wounded more than 10 others in twin attacks on two schools in the southeastern city of Aracruz, in Espirito Santo state.
The country’s deadliest school shooting left 12 children dead in 2011, when a man opened fire at his former elementary school in the Rio de Janeiro suburb of Realengo, then killed himself.
There have also been a series of cases of deadly violence at preschools.
In 2017, a guard at a preschool in the southeastern town of Janauba doused a group of children and himself in alcohol and set them on fire, killing nine children and a teacher and leaving around 40 wounded.
Authorities said the man, who also died, suffered from “mental problems.”
In 2021, an 18-year-old man killed three young children and two employees in a knife attack on a preschool in the town of Saudades, Santa Catarina, the same state where Wednesday’s attack occurred.
AFP