A man who opened fire in central Vienna on Monday night while armed with an automatic rifle, a pistol and a machete and wearing a fake explosive device was a 20-year-old Austrian citizen who had sought to travel to Syria to join the Islamic State group, Interior Minister Karl Nehammer said in a news briefing Tuesday.

The rampage left four dead and 22 others wounded in the heart of the Austrian capital before the gunman was killed by police nine minutes after the assault began, Nehammer said, adding that the evidence gathered so far showed no indication that others were involved.

The minister said that the suspect had been arrested once before after trying to travel to Syria to join the Islamic State group. The man was sentenced to 22 months in prison for that attempt but was released early, raising questions about how someone on the radar of authorities had managed to carry out such an attack.

Austrians vowed that the attacker would not divide their society or destroy their democracy. Chancellor Sebastian Kurz said in an address to the nation Tuesday morning that the shooting was “definitely an Islamist terrorist attack,” which he called “an attack out of hatred, hatred for our basic values.”

“We often see ourselves as a blessed island where violence and terror is only known from abroad,” he said. “But the sad truth is: Even if we live in a generally safe country, we don’t live in a safe world.”

Austria’s government announced a three-day period of official mourning beginning Tuesday, in which flags on public buildings will be lowered to half-staff. A minute’s silence was held at noon.

On Tuesday morning, Harald Sörös, an Interior Ministry spokesman, said that a second woman had died of her injuries, bringing the number of victims to four. Twenty-two people were wounded, Nehammer later confirmed.

Monday’s violence comes after recent terror attacks in France — including the beheading of a teacher and a knife attack at a church — that have both been linked to Islamist extremists. But Kurz warned against making assumptions about the Muslim community.

“This is no fight between Christians and Muslims, or between Austrians and migrants,” he said. “This is a fight between civilization and barbarism.”

Ümit Vural, president of the Islamic Faith Community in Austria, condemned the “cowardly, revolting attack,” calling it “an attack on our Vienna” and “an attack on all of us.”

“Our democracy, our freedom and liberal order is stronger than violence and terror,” he said.

What do we know about the gunman who was killed and the others arrested?

The attacker was a 20-year-old Vienna-born man, who is ethnically Albanian and whose parents came from North Macedonia, Nehammer said Tuesday. The man was known to authorities and had previously been convicted of attempted jihad and attempted membership in a terror organization, after he tried — and failed — to travel to Syria to join the Islamic State.

The man was sentenced to 22 months in prison but only served a few, Nehammer said. Evidence found in the suspect’s home, including a stockpile of munitions, indicated that he had lived a split life — presenting himself to the world as fully integrated into society, while clearly embracing radicalism in private, the minister said.

“There were no warning signs about his radicalization,” Nehammer added, vowing to review the justice system to try to ensure that a similar situation would not happen again.

Before the attack, the man posted a photograph of himself to social media, wielding a machete and a rifle with a message that “clearly indicated his sympathy for IS,” the minister said, using an abbreviation for the Islamic State.

Nikolaus Rast, who represented the man when he was on trial in 2018 for attempting to travel to Syria to join the Islamic State, said that there had been no indication that he was dangerous. His client had planned to travel to Syria to join the extremist group with a friend, but he only got as far as Turkey and was soon arrested and taken back to Austria, Rast said.

There had been no sign that his parents shared his extremist views, and the man’s mother had been the one to alert authorities when her son first went missing at that time, Rast added.

Rast said that his client’s remorse after returning to Austria seemed genuine and that his behavior in prison was such that he was released after only about a year of his 22-month sentence. The man took part in a special de-radicalization program, the lawyer added.

“He gave the impression of a young man who was searching for who he was,” Rast said. “At no point did I have the impression that he was dangerous.”

At least 14 people who are linked to the suspect have been detained and are being questioned, and 18 locations are being searched, Nehammer said in the afternoon briefing. Several raids were carried out, mostly in Vienna, but also in St. Pölten, an hour west of the city, and in Linz, about 115 miles west of the capital.

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The view from Vienna, a bustling capital gone quiet.

The cobbled streets of the center of Vienna, normally full of tourists, government employees and other citizens, was largely empty Tuesday, save for hundreds of heavily armed police officers. School attendance was optional and residents were encouraged to stay home.

Church bells rang out at noon, as the city paused for a moment to honor the victims. Among them, Austria’s largest church bell — the “Pummerin,” which hangs in the northern tower of St. Stephen’s Cathedral and is only used for special events — rang out.

The attack Monday came hours before the country entered a lockdown to combat the coronavirus, with many people having gathered outdoors in Vienna before it came into force. Hundreds of others were trapped in the city’s famed opera house and the national theater, both of which were evacuated by police hours after the curtains had fallen.

“You could feel a lot of people wanted to get out one more time before lockdown starts,” said Ameli Pietsch, 23, who was in the area an hour before the attack. “It was a mild evening and lots of people were outside.”

All of that changed in a moment. People scrambled from the streets to shelter in restaurants, and all trams and subways in the city’s center were halted as police urged residents to shelter in place.

The sound of sirens and helicopters filled the night air as people struggled to absorb what was happening.

Said Farnaz Alavi, 34, a human resources consultant in Vienna, said, “We are in shock.”

Kurz said in his speech Tuesday morning that the gunman had killed four people at close range — an older man, an older woman, a younger man passing by and a waitress working in a restaurant.

But he also urged citizens to remember that “our enemy is never all those belonging to a religion, our enemy is never all the people that come from a particular country” but rather “our enemy is extremists and terrorists.”

“They do not belong in our society,” he added.

With the target unclear, authorities discouraged speculation.

The area where shots were first reported is a tight web of streets packed with bars and pubs, known locally as the “Bermuda Triangle.” It is also home to Vienna’s main temple, the Seitenstettengasse synagogue. But the attack’s intended target, or targets, was unclear.

The president of the Jewish Religious Community in Austria, Oskar Deutsch, said on Twitter that the initial shooting had occurred “in the immediate vicinity” of the temple, but that it was closed at the time.

“It is not clear right now whether the main temple was the target,” he said. Jewish institutions across the city were closed Tuesday, the Jewish Community of Vienna said on its website.

Police took to Twitter to urge restraint.

“Please don’t share any rumors, accusations, speculations or unconfirmed numbers of victims,” they said. “That does not help at all! Stay inside, take shelter. Keep away from public places.”

As news of the attack unfolded, several people posted dramatic videos on social media of what appeared to be the shooting and its aftermath.

One showed people helping a wounded person who was lying in a pool of blood, just outside a restaurant on Ruprechtsplatz and less than a mile from the Austrian Parliament. Several chairs in the restaurant’s outdoor area had been overturned, as if abandoned in a hurry.

Another video showed a man emerging from a bar or restaurant, then firing a rifle twice down a street. And a separate video appeared to show the same gunman on the same street, shooting a man with a long gun at close range, then returning seconds later to shoot him twice more.

Vienna police, in a post on Twitter, pleaded with witnesses not to post videos and pictures to social media, but instead to send them to the authorities.

The city has found itself in the crosshairs before.

Austria — and Vienna in particular — has been a target over the years for terrorist attacks, often with deadly outcomes. Religious and political tensions, sometimes with no clear connection to Austria, have led to sporadic violence.

In 1975, a meeting of OPEC in the city was stormed by six men with submachine guns. They killed three people and took at least 60 hostages.

A group that claimed responsibility cast the attack as “an act of political contestation and information” aimed at “the alliance between American imperialism and the capitulating reactionary forces in the Arab homeland.”

In 1981, Heinz Nittel, a leader of the Austrian Socialist party and head of the Austria-Israel Friendship Society, was assassinated outside his home by an assailant associated with a militant Palestinian group.

Two people were killed in 1981 when terrorists attacked a synagogue with grenades and firearms. Just after Christmas in 1985, panic engulfed the Vienna airport when three gunmen stormed the check-in lounge and opened fire with submachine guns, killing three and wounding dozens.

Witnesses at the time said the attack began as an El Al Israel Airlines flight was boarding. The attack appeared to be coordinated with another El Al check-in 10 minutes earlier in Rome.

From 1993 to 1997, a series of mail bombs and other explosive devices, including one that wounded the mayor of Vienna, stoked fears of rising neo-Nazi terrorism in the country. The man who was convicted in the attacks said that his goal had been to create a reunification of German-speaking areas.

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