At least four people were killed and 17 others wounded, seven with life-threatening injuries, in a shooting spree in the city center of Vienna, Austria, on Monday, before police shot and killed a gunman the country's interior minister described as an "Islamist terrorist."

Austria's interior minister Karl Nehammer said two men and two women died from their injuries, according to The Associated Press. Nehammer said a single suspect, armed with a rifle and fake explosive vest, was killed by police.

"We experienced an attack last night by at least one Islamist terrorist," Nehammer said. He later said the suspect was a 20-year-old dual citizen of Austria and North Macedonia who had a previous "terror conviction," according to the AP.

Nehammer said the suspect's house had been searched and video material seized. Several additional arrests were made and at least 15 additional homes searched.

Residents of Vienna were told to stay home on Tuesday as authorities tried to determine whether there were other attackers or accomplices.

The incident began at about 8 p.m. (2 p.m. ET) Monday when at least one gunman opened fire near Vienna's main synagogue. The synagogue was closed and unoccupied at the time.

Witnesses said the gunman fired randomly into bars and cafes which were crowded on the last night before a nationwide lockdown because of the coronavirus. The gunman was killed by police within minutes.

Austrian Chancellor Sebastian Kurz described the incident as a "despicable terror attack." The government declared three days of national mourning with flags to be flown at half-staff through Thursday. Tuesday at noon (6 a.m. ET) the nation will observe a minute of silence.

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