The suspected shooter, a 13-year-old boy, surrendered on Wednesday, police said, after taking two handguns belonging to his father and killing eight pupils and a security guard in their school in the capital Belgrade.

A teacher and six pupils were wounded. They are being treated in the Tirsova hospital and the city’s University Hospital.

“The girl who underwent an urgent surgery yesterday due to head injuries … remains in critical condition and in intensive care,” Sinisa Ducic, the acting director at the city’s Tirsova hospital, told reporters.

Milika Asanin, director of the University hospital, said that the condition of a severely wounded boy treated there had improved, but was still considered critical, the Tanjug news agency reported.

The remaining children and the teacher treated in the two hospitals were in stable condition, both Ducic and Asanin said.

Mass shootings in Serbia are rare and this was the first-ever school shooting in the Balkan country, prompting the government to announce tougher curbs on gun ownership and to declare three days of national mourning from Friday.

President Aleksandar Vucic on Wednesday announced a moratorium on new gun licences other than for hunting, a revision of existing permits, enhanced surveillance of shooting ranges and of how members of the public store their weapons.

In a statement on Thursday, the Serbian Interior Ministry warned gun owners to keep their weapons empty and locked up.

Police will control homes of gun owners to ensure they keep weapons properly. Negligently stored arms will be confiscated and owners will face charges, the ministry said.

The suspected shooter used two pistols that belonged to his father, police said on Wednesday. The guard and three girls were shot in a hallway. A teacher and pupils in a history class were then shot, police said.

Porfirije, the patriarch of the Serbian Orthodox Church, called for a memorial prayer on Thursday.

The suspected shooter is under Serbia’s age of criminal responsibility. He has been in a psychiatric institution for an evaluation, Vucic told reporters on Wednesday, adding the suspect’s parents had been arrested.

Irina Borovic, a lawyer for the shooter’s father, told Reuters that her client was to face charges of aggravated endangering of public safety and will appear before the court on Friday.

A day after the shooting, residents in Belgrade were still coming to terms with what happened. Aleksandra Zizic, a schoolteacher, said she was in shock.

“We have spent the day yesterday with children to try and rationalise … what happened. But there are no words,” she told Reuters.