The attack began at about 3:00 PM, when the man drove into the square and opened fire on pedestrians with a military-type long gun. Police described a "wild ride" around the square, and he is reported to have wounded people at more than one location. He wore military-style fatigues and a bulletproof vest. Officers confronted him in a gunfight in which he kept firing after being hit, and he was stopped near the intersection of Stradomska and Dietla Streets. Police later found more weapons and ammunition in his vehicle.

Two police officers were among the wounded. One was in "very serious condition" with multiple gunshot wounds, police said. Two horses were also shot and both survived. The reported number of injured varies by a person or two depending on whether the attacker is counted. The death toll was first given as five before being raised to six.

Inside the shops around the square, staff sheltered customers. One boutique worker said she locked 10 people in her store and turned off the lights until the threat passed.

Interior Minister Marcin Kierwiński said the attacker was "fascinated with far-right ideologies" and held "very radical views" that he described as "ultra-nationalistic." Defense Minister Władysław Kosiniak-Kamysz called the shooting an "act of terror" and said all circumstances and motives are being investigated.

Krakow Mayor Łukasz Gibała declared mourning in the city until Wednesday and said Krakow would remain open to visitors, who number about 15 million a year. President Karol Nawrocki began the formal procedure for national mourning on Sunday and Monday and offered condolences to the victims' families. Prime Minister Donald Tusk praised the police response. In Warsaw, about 250 km away, Mayor Rafał Trzaskowski announced added security measures, including road barriers in the Old Town. U.S. Ambassador to Poland Tom Rose, writing on X, condemned a "savage and murderous attack" and a "horrific mass shooting" and expressed solidarity with Poland.

Mass shootings are rare in Poland, where about 411,000 people hold gun permits in a population of 37 million. In mid-October, three school attacks in Mazovia province left one person dead and several injured.