A man killed two policewomen and a bystander in the Belgian city of Liege, Reuters news agency reports.

Named by public broadcaster RTBF as a 36-year-old petty criminal let out on day-release from a local prison, the gunman shouted “Allahu Akbar,” according to a police source. Investigators are looking into whether he converted to Islam while in prison.

The attacker approached the policewomen from behind with a box-cutter knife around 10:30 a.m. (0830 GMT) in downtown Liege. After stabbing both policewomen, the man seized one of their guns and shot them both dead. Having killed them, the attacker walked down the street and shot dead a 22-year-old man sitting in the passenger seat of a parked car.

After shooting the man, he walked into a nearby high school and took a female employee hostage. This, according to Reuters, triggered a major intervention by the police. A gun battle between the police and the attacker broke out, which sent people in the street racing for cover. High school students were moved to safety.

“The event is classed as a terrorist incident,” public prosecutor Philippe Dulieu said.

Expressing his condolences to the families of the victims, Belgium’s Prime Minister Charles Michel said it was too early to say what had caused the attack.

Featured image credit: Geert Vanden Wijngaert AP Images

According to the New York Daily News, Belgian media identified the attacker as Benjamin Herman. No injuries were reported to the hostage taken at the Athénée Léonie de Waha high school in Liege. The attacker, previously known to the authorities for drug and theft crimes, may have been radicalized in prison.

A Brussels-based Islamic State cell was involved in terrorist attacks in the Belgian capital in 2016 when 32 people died. The same cell is responsible for the death of 130 Parisians in 2015, Reuters noted. European authorities are, according to the same outlet, concerned about the risk of petty criminals being radicalized and inspired to Islamist violence while in prison.

“The individual has been neutralized,” Hervé Jamar, the governor of the Province of Liège said on Twitter, according to the New York Times. The same publication reports that the attacker, after taking a cleaning lady at the Athénée Léonie de Waha high school hostage, had opened fire once law enforcement moved in, wounding two further police officers.

The cleaner the attacker had taken hostage was not injured, and the students were brought to safety to a nearby park and moved to another public school building.

A similar attack occurred in Liege in 2011 when a gunman wounded multiple individuals, killed four, and then shot himself.

Belgium’s crisis center, according to the New York Times, said a security cordon had been placed around parts of the city and the citizens have been warned to avoid the area.