Three people, including a 14-year-old girl, died on Thursday after a gunman wearing a bulletproof vest opened fire and set a hospital and an apartment ablaze in the Dutch city of Rotterdam, police said.

The shooting sent patients and medics fleeing the Erasmus Medical Center in downtown Rotterdam, including some who were wheeled out of the building in beds. Others barricaded themselves into rooms and stuck hand-written signs to windows to show their location.

Police Chief Fred Westerbeke told reporters that the shooter was a 32-year-old student from Rotterdam. He was arrested at the hospital carrying a firearm. His identity was not released, and the motive for the shootings was still under investigation.

He first shot and killed a 39-year-old woman and seriously injured her 14-year-old daughter at an apartment close to where the suspect lived, Westerbeke said. Police said the girl later died of her injuries.

The shooter then went to the nearby Erasmus Medical Center, where he shot and killed a 46-year-old man, a teacher at the academic hospital, the police chief added. He also started fires at the scenes of both shootings.

The identities of the victims were not released.

The suspect was cooperating with police, Westerbeke said.

"We cannot say anything about the motive of this terrible act at this time. The probe is still ongoing," chief public prosecutor Hugo Hillenaar told reporters.

The suspect was arrested under the hospital's helipad, and police said they did not believe any other shooters were involved.

The suspect, a student at the hospital, was already known to the authorities over a conviction for animal cruelty, police said.

"The suspect was known to law enforcement and in 2021 he was prosecuted and convicted for animal abuse," Hillenaar said.

An investigation is underway as to whether he was a student of the teacher shot dead. Authorities believe that the woman and her daughter were close neighbors of the suspect, leading Westerbeke to suggest they were "targeted attacks."

"I am angry and sad," said Rotterdam Mayor Ahmed Aboutaleb. "It was a black day."

"We have been shocked by a horrible incident. Shots were fired in two different places in the city. Many people witnessed it," the mayor told reporters.

"Emotions in the city are very high. My condolences go out to the victims."

'Panic and screaming'

Witnesses described the chaotic scenes around the hospital, as helicopters buzzed overhead and police snipers took up positions on the hospital roof.

"First, there was a shooting on the fourth floor. Four or five shots were fired. Then a Molotov cocktail was thrown into the education center," said a medical student quoted by RTL Nieuws, who did not give his name.

"There was a lot of panic and screaming... I didn't hear any shots, just the panic, and that's what I started to act on," public broadcaster NOS cited another eyewitness as saying.

Prime Minister Mark Rutte spoke of his "great dismay" at the shootings.

"My thoughts go out to the victims of the violence, their loved ones, and all those who have been hugely scared," he added in a statement on X, formerly Twitter.

Dutch King Willem-Alexander and Queen Maxima expressed their sympathy on social media.

"Our hearts go out to the family and friends of the victims of the violence this afternoon in Rotterdam," the royal pair wrote. "We also think of everybody who lived in fear during these terrible actions," they added.

"It's unbelievable," said Rotterdam GP Matthijs van der Poel, cited on the Algemeen Dagblad website.

"Everyone is totally shocked by the events and is watching the news with horror. I'm afraid such things cannot be prevented," he said.

The Erasmus Medical Center appealed on social media for people not to go to the hospital, but later said it was reopening. It said that all appointments scheduled for Friday would go ahead as planned.

There have been scores of small explosions at homes and businesses across Rotterdam this year, blamed on rival drug gangs. There was no immediate suggestion that Thursday's shooting was linked to the feuding drug gangs.

In 2019, three people were shot dead on a tram in Utrecht, sparking a massive manhunt.

In 2011, the country was left shocked when 24-year-old Tristan van der Vlis killed six people and wounded ten others in a rampage at a packed shopping mall.