VIENNA — At least one Islamic extremist — a 20-year-old armed with an automatic rifle and a fake explosive vest — rampaged through a crowded Vienna nightlife district hours ahead of a coronavirus lockdown, leaving four people dead before being killed by police, Austrian authorities said Tuesday.

The suspect in Monday night's attack was identified as a young Austrian-North Macedonian dual citizen with a previous terror conviction for attempting to join the Islamic State extremist group in Syria. 

Unverified video showed the suspect, dressed in white coveralls, firing off bursts apparently at random as he ran down the Austrian capital's cobblestone streets. 

Police have arrested several other people and searched 15 houses and apartments, Interior Minister Karl Nehammer told the Austrian news agency APA. 

Two men and two women died from their injuries in the attack, Chancellor Sebastian Kurz said. He said a police officer who tried to get in the way of the attacker was shot and wounded, and another 14 people were hurt.

Vienna's hospital service said seven people were in life-threatening condition Tuesday after the attack, APA reported.

"Yesterday's attack was clearly an Islamist terror attack," Kurz said. "It was an attack out of hatred — hatred for our fundamental values, hatred for our way of life, hatred for our democracy in which all people have equal rights and dignity."

The attacker, identified as Kujtim Fejzulai, was sentenced to 22 months in prison in April 2019 because he had tried to travel to Syria to join the Islamic State group. He was granted early release in December under juvenile law.

Nehammer told APA that Fejzulai had posted a photo on his Instagram account before the attack that showed him with two of the weapons he apparently used.

"(The suspect) was equipped with a fake explosive vest and and an automatic rifle, a handgun and a machete to carry out this repugnant attack on innocent citizens," Nehammer said.

Authorities were still trying to determine whether further attackers may be on the run. People in Vienna were urged to stay at home if possible on Tuesday and children did not have to go to school. Some 1,000 police officers were on duty in the city on Tuesday morning.

The shooting began shortly after 8 p.m. (1900 GMT) Monday near Vienna's main synagogue as many people were enjoying a last night of open restaurants and bars before a month-long coronavirus lockdown, which started at midnight.

Vienna police chief Gerhard Puerstl said the attacker was killed at 8:09 p.m. But authorities continued to look for potential further assailants.

"We will unearth and chase down the perpetrators, those behind them and like-minded people and give them the punishment they deserve," Kurz said. "We will pursue all those who have anything to do with this outrage by all available means."

His government on Tuesday ordered three days of official mourning, with flags on public buildings to be flown at half-staff until Thursday, APA reported. 

Austria held a minute of silence at midday Tuesday, accompanied by the tolling of bells in the capital. Kurz, President Alexander Van der Bellen and other leading politicians laid wreaths and candles in the area where the attack took place.

Rabbi Schlomo Hofmeister said he saw at least one person shoot at people sitting outside at bars in the street below his window near the city's main synagogue.

"They were shooting at least 100 rounds just outside our building," Hofmeister said. "All these bars have tables outside. This evening is the last evening before the lockdown." 

Authorities said residents have uploaded 20,000 videos of the attack to help police with their investigation.

The attack drew swift condemnation and assurances of support from leaders around Europe, including from French President Emmanuel Macron, whose country has experienced three Islamist attacks in recent weeks, and German Chancellor Angela Merkel.

U.S. President Donald Trump tweeted Monday night as he prepared for his final rally ahead of Election Day: "Our prayers are with the people of Vienna after yet another vile act of terrorism in Europe."

"These evil attacks against innocent people must stop," Trump added. "The U.S. stands with Austria, France, and all of Europe in the fight against terrorists, including radical Islamic terrorists."

Egypt's Al-Azhar, the Sunni Muslim world's foremost religious institution, condemned the "terrorist attacks" in Vienna. It called on international institutions "to stand united" against terrorism and reject violence and hatred.

Austria's military sent 75 soldiers to guard key sites in Vienna, freeing up police to continue the investigation.