A 12-year-old student suspected of shooting dead a classmate and injuring two others in Finland told the police that he had been bullied at school, officials said Wednesday, as the nation shocked by the attack held a day of mourning.

The suspect, a sixth grader who attended the school in the city of Vantaa, just outside Helsinki, was apprehended less than an hour following the shooting on Tuesday morning.

The shooter and the victims were all classmates, the police said.

“The motive for the act has been found to be bullying,” the Eastern Uusimaa Police Department, which is in charge of the investigation, said in a statement.

“The suspect has said during interrogations that he was the target of bullying, and this information has also been confirmed in the investigation by the police. The suspect had transferred to Viertola school at the beginning of this year.”

The minimum age of criminal liability in Finland is 15 years, which means the suspect cannot be formally arrested. A suspect younger than 15 can only be questioned by the police before they are handed over to child welfare authorities.

On Wednesday, Finnish blue-and-white flags were hoisted at half-staff and scores of people including parents, teachers and fellow students laid flowers and lit candles in the snowy landscape near the school building where the shooting occurred.

Police said one of the wounded girls has a serious condition.

The deceased boy died instantly after being shot, police said. The suspect was detained in the Helsinki area less than an hour after the shooting with a “a revolver-like handgun” in his possession. The gun was licensed to a relative of the suspect who was not immediately identified. Police said he admitted to the shooting in an initial police hearing.

Finland has witnessed two major deadly school shootings in 2007 and 2008. In their wake, the country tightened its gun laws, raising the minimum age for firearms ownership and giving police greater powers to perform background checks on individuals applying for a gun license.

The nation of 5.6 million has more than 1.5 million licensed firearms, and about 430,000 license holders, according to the Finnish Interior Ministry. Hunting and gun-ownership are deeply rooted traditions in this sparsely-populated northern European country, where target practice is also a widespread hobby.