Austria has released the first details known about the attacker who was killed by police in Vienna during Monday night’s mass shooting. The attacker, who killed four people and wounded 22 others in the heart of Austria’s capital, has been identified as 20-year-old Kujtim Fejzulai, an Austrian-North Macedonian dual national who had a previous terror conviction, according to the Associated Press. Four individuals died and at least 21 more were injured in the Monday night attack. Authorities said a police officer who tried to intervene was among the wounded.

Interior Minister Karl Nehammer said his government’s initial investigations show the suspect sympathized with ISIS, saying: “We experienced an attack last night by at least one Islamist terrorist.” The minister added that arrests have been made following raids at addresses linked to the dead attacker. Sebastian Kurz, the chancellor of Austria, wrote Tuesday morning: “It has now been confirmed that it was an Islamist terrorist attack. It was a hate attack.” Nehammer added that 14 people had been taken into “provisional” custody in the investigation and that there was no evidence of a second perpetrator as of Tuesday.