A gunman who killed at least six people during a deadly rampage in the Polish city of Kraków on Saturday has died in hospital, Reuters news agency reported on Monday, citing police.

The country was horrified by the rare mass shooting in the historic main square of the city in the country’s south, which prompted national mourning and heightened security, as authorities said the attack was likely driven by far-right ideology.

The Polish citizen, in his 20s, was shot and injured by police during the attack before being transported to hospital. There, he underwent multiple surgeries and had been in a critical condition prior to his death.

The mass shooting — which authorities said they are investigating as a possible terror attack — has generated a wave of fear in a European nation with exceptionally tight gun laws.