A teenager who killed eight fellow students and a security guard in a Serbian school planned the attack for weeks and had a “kill list”, according to police.
The 13-year-old was arrested following Wednesday morning’s attack at the Vladislav Ribnikar primary school in central Belgrade.
Another six pupils and a teacher were also injured in the shooting.
The motive for the attack is still being investigated, police said.
Officers in helmets and bulletproof vests cordoned off the area around the school, located in the central Vracar neighbourhood, shortly after 08:40 (06:40 GMT).
The suspect, named by police as Kosta Kecmanovic, is alleged to have used his father’s guns, both of which had legal permits. He is also said to have gone to a shooting range more than once with his father before the killings.
In a televised address to the country, President Aleksandar Vucic described the attack as “the most difficult day in the modern history of our country”.
He said the suspect would be sent to a psychiatric clinic. Under current Serbian law, he cannot be held criminally responsible as he is under 14.
Mr Vucic has suggested that the age of criminal liability may be lowered to 12 in the wake of the killings.
He has also proposed several other reforms, including an audit on firearms licences and a tightening of the rules around who can access shooting ranges. (BCC)