One person was killed and four others were injured when a 31-year-old Ukrainian man allegedly attacked clergy and worshippers with a knife at a Benedictine abbey in Jaroslaw, southern Poland.

Police said the suspect entered the country from Germany earlier that day, took a knife from the abbey’s kitchen and attacked four men and one woman, including a priest in a confessional.

Three of the victims were clergy members, and two remained in critical, life-threatening condition.

The motive remains unclear, while prosecutors said the suspect had been heading toward a border crossing with Ukraine before going to the abbey, Al-Jazeera has reported.

Polish and Ukrainian leaders condemned the attack, and the mayor of Jaroslaw declared a period of mourning as authorities investigate.