A 13-year-old boy opened fire on his classmates at a school in the Serbian capital Belgrade Wednesday, killing at least eight children — one boy and seven girls — along with a security guard. How it happened: After arriving early morning at the Vladislav Ribnikar Elementary School, a well-known institution in Vračar, an upscale area of the Serbian capital, the teenage suspect “immediately pulled the pistol out of his bag” and shot the school’s security guard before he went on to take the lives of the eight schoolmates and injuring six others and a teacher, Belgrade's Police Chief Veselin Milić said. The suspect called police: “He left the classroom, went out into the schoolyard, releasing the magazine from the weapon, throwing it down the steps,” Milić said Wednesday, adding the suspect called the police himself and waited until he was arrested in the yard. About the suspect: The teenage suspect was a student at the school, authorities said. Possession of weapons: The suspect had two guns, Serbian Interior Minister Bratislav Gasic said at a news conference: “The parent had several pieces of weapon and kept them locked up. The safe had a code. Obviously the kid had the code as soon as he managed to get hold of those two guns. And three frames full of 15 bullets each,” authorities said. Separately, the boy had a 9mm pistol as well as a small calibre pistol in a bag, as well as four Molotov cocktails, Milić added. What happens next: The suspect's father was arrested Wednesday, the Higher Public Prosecutor’s Office in Belgrade said. The mother was also arrested, according to Serbian President Aleksandar Vucic. The 13-year-old suspect will not be held criminally responsible as he has not reached the age of 14, the prosecutor's office said, adding that this aligns with Serbia’s Law on Juvenile Offenders and the Criminal Legal Protection of Minors. The suspect would be placed in a special psychiatric institution, the president said.