A gunman killed two police officers and a passerby on Tuesday before being shot dead in Belgium’s Liege city, the country’s public broadcaster RTBF reported. A woman was taken hostage during the attack, and two police personnel were injured.

The shooting took place around 10:30 am local time (2 pm Indian Standard Time) near a high school, reported France 24.

A spokesperson from the Liege prosecutor’s office told CNN that it is not yet clear what the attacker’s motive was. The country’s anti-terrorist crisis centre has, however, taken over the investigation. “It [terrorism] is one of the questions on the table, but for the moment all scenarios are open,” a spokesperson for the centre told Reuters.

The shooter, identified as Benjamin Herman, was on prison leave since Monday, RTBF reported quoting unnamed officials. He was serving a sentence for theft, damage to public property and drug trafficking. It is suspected that Herman was radicalised while serving time in prison in Lantin town, the broadcaster said.

Belgium’s Prime Minister Charles Michel said he was following the situation closely and expressed his support for the victims of the shooting, reported BBC.

The country has been on high alert since a Brussels-based Islamic State cell was involved in attacks on France’s Capital Paris in 2015 in which 130 people were killed. An attack in Brussels in 2016 in led to 32 deaths.