A Polish man who killed six people in Krakow's main square on November 7 researched Norwegian white supremacist Anders Behring Breivik, according to Poland's Justice Minister Waldemar Zurek. Zurek stated on Tuesday that there was "a very strong indication of right-wing extremism" behind the attack.

The shooting, which occurred in Krakow's historic main square, a popular tourist destination, has shaken the nation. Investigators also found a Gadsden flag, often associated with the US far-right, among the suspect's possessions.

Prosecutors identified the suspect as 24-year-old factory worker Michal Oksinski. He died in hospital on Monday after being shot by police during his arrest minutes after the shooting. A silencer was discovered in the car he used during the attack.

The bodies of Oksinski’s father, mother, and sister were found at their family home on Saturday, and officials believe they were also killed by him. In July 2011, Anders Behring Breivik killed eight people with a car bomb in Oslo and then shot and killed 69 others, mostly teenagers, at a Labour Party youth camp.

The suspect's motives have become a point of political contention. Interior Minister Marcin Kierwinski initially suggested far-right ideology influenced the gunman, a statement that was called a "blatant lie" by Jaroslaw Kaczynski, leader of the opposition Law and Justice (PiS) party. Government members appeared to temper their statements on Monday.

Right-wing PiS lawmaker Michal Wojcik expressed outrage at Justice Minister Zurek's comments, telling Reuters that he believed "representatives of the Polish government are acting dishonestly toward the international community."

Kierwinski, however, told public radio on Tuesday that he stood by his earlier remarks and was awaiting the official findings from investigators.

The incident has led to national mourning, with political rivals participating in a 'March of Silence' for the victims.