(CNN) At least three people were killed and 11 others injured Friday after a gunman opened fire at two schools in the Brazilian state of Espirito Santo, according to local authorities.
The attacks took place in the small town of Aracruz, 50 miles north of the state capital, Vitoria.
The alleged shooter -- who was seen in security footage carrying a semi-automatic weapon, wearing military attire and a face covering -- has been arrested by police. The suspect has not yet been identified by authorities, but local media, including CNN affiliate CNN Brasil, have reported the individual to be a 16-year-old.
Espirito Santo governor Renato Casagrande, in a Twitter post Friday, confirmed "security teams caught up with the attacker who, cowardly, attacked two schools in Aracruz. I declared three days of official mourning as a sign of grief for the irreparable losses. We will continue to investigate the reasons and, soon, we will have new clarifications."
The governor said the attacks took place at the Primo Bitti school and the Praia de Coqueiral Educational Center.
Speaking to the media, Public Safety minister Marcio Celante said police believe the suspect acted alone based on security video, but acknowledged further investigation was needed to ascertain more details on the incidents.
Celante also revealed some of what the security video showed.
"The first criminal action was to access the school by breaking the padlock. He had access to the teachers' room," Celante said, adding that "afterwards, he moved to another school, where he made more victims."
Brazil's president-elect, Luiz Inacio Lula da Silva, called the incident an "absurd tragedy."
"It's with sadness that I was informed about the attacks at the Aracruz schools in Espirito Santo. My solidarity goes to the family of the victims in this absurd tragedy," Lula tweeted.
"My support goes out to Governor Casagrande in investigating the case and comforting the communities surrounding the two affected schools," he added.
Brazilian minister Victor Godoy also joined his government peers in expressing his sympathies.
"My condolences to the parents, relatives and employees of the Primo Bitti State Elementary and Middle School and the Praia de Coqueiral Educational Center, in Aracruz. I submit for the record my repudiation of this manifestation of violence," Godoy wrote on Twitter.