Austrian police arrested 14 people and searched 18 locations as part of a huge dragnet on Tuesday after a gunman killed four in a rampage in Vienna overnight.
Officials said there was no indication that more than one attacker was involved in the shootings after previously saying they believed there could be up to four attackers.
"The videos evaluated so far do not reveal any evidence of a second perpetrator. Because the evaluation has not yet been completed, however, we cannot finally say how many perpetrators are actually responsible for the crime," said Austrian Interior Minister Karl Nehammer.
The 14 people arrested are being questioned, according to the Interior Ministry.
One suspect armed with an assault rifle and handguns and wearing a dummy explosive vest was killed in the Monday evening incident, officials said.
The Interior Ministry identified the suspect who was killed as Fejzulai Kujtim, 20. He had North Macedonian roots and a criminal record for affiliation with a terrorist organization, officials said.
He was killed nine minutes after police were called, police said Tuesday afternoon.
Nehammer said Kujtim was a sympathizer of the Islamic State militant group. Police said they have searched Kujtim's apartment though they did not give details of what they found. Officials are also combing through video footage of the event.
Later on Tuesday, the Islamic State group claimed responsibility for the Vienna attack in a statement via Aamaq, its media arm, according to Flashpoint Intelligence, which tracks ISIS social media for NBC News.
The shooting took place on the last night before Austria's second coronavirus lockdown was set to begin, restricting access to nonessential businesses until the end of November.
The number of injured rose Tuesday afternoon to 22 from 14 announced earlier in the day. People in Vienna were urged to stay at home if possible and children did not have to go to school.
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Shlomo Hofmeister, a rabbi in Vienna, said he witnessed the attack from his home in the lively city center, which is full of bars and restaurants and also home to the main synagogue.
“I saw a man heavily armed with a long weapon standing right below my window shooting at the crowds. He was shooting at where the crowds were sitting,” he said.
When police arrived at the scene, Hofmeister said they called out looking for people who were injured. He said he heard people shouting from inside bars and restaurants that they had been hurt.
Austria held a minute of silence at noon (6 a.m. ET) to remember the victims of the attack.
The attack took place just days after an attack on a church in Nice, France, that killed three people. Authorities believe a 21-year-old Tunisian national who entered France in early October began stabbing people after he entered the Notre Dame basilica Thursday morning.
The incident in Nice is being investigated as a suspected terror attack.
The Austrian government Tuesday ordered three days of official mourning, with flags on public buildings to be flown at half-staff until Thursday, the APA reported. A minute of silence was to be held at noon Tuesday.
Leaders from around the world sent condolences to Austria, including President Donald Trump.
“Our prayers are with the people of Vienna after yet another vile act of terrorism in Europe,” he wrote on Twitter.
Reuters contributed to this report.