A terrorist posed with guns before killing four people and injuring 22 in Vienna.
Kujtim Fejzulai, 20, was arrested in 2019 for joining ISIS, sentenced to 22 months in prison but was released just seven months later.
A photo of Fejzulai posing with an automatic rifle, handgun and a machete was shared for the first time, hours before the attack.
The 20-year-old posted the image on his Instagram account pledging his allegiance to ISIS leader Abu Ibrahim al-Hashimi al-Quarashi.
The attack began at 8pm on Monday night in the Austrian capital, where several men armed with rifles fired openly outside Vienna's main synagogue.
"It sounded like firecrackers, then we realised it was shots," a witness told ORF.
The terrorist had "shot wildly with an automatic weapon" before he was 'neutralised' - shot dead by police at 8:09 pm.
Authorities are still trying to determine whether further attackers may be on the run.
UK Prime Minister Boris Johnson said he was "deeply shocked' at the attacks, and said Britain stood united with Austria against terror.
Prime Minister of the Netherlands Mark Rutte called this a "heinous act".
"Our thoughts are with the victims and their families, and with the Austrian government in dealing with this heinous act," he wrote on Twitter.
