Polish Justice Minister Waldemar Zurek issued an update on Tuesday concerning the case of a mass shooting in Krakow over the weekend.

Accused gunman Michal Oksinski was deeply interested in international far-right movements, Zurek said.

"Authorities have accessed the terrorist's computer. It is clear that he visited websites concerning Anders Breivik," the Norwegian neo-Nazi who killed 77 people in July 2011, the minister added.

Zurek said a search of Oksinski's home turned up a Gadsen flag, a banner dating back to the US Civil War that is now associated with American white nationalists.

Police also gathered evidence that he had recently bought 10 magazines for a semi-automatic rifle and 500 bullets.

"It is clear that this individual was preparing to take action," the justice minister said.

What happened in the attack?

On Friday night, 24-year-old Oksinski is thought to have shot and killed his mother, father, sister and two family cats in the city of Ostrowiec. 

The following day at around 3:00 p.m. local time, Oksinski is suspected of opening fire in Krakow's Main Market Square. Six people were killed — four Poles, one Austrian, and one UK national. Another 15 people were wounded. 

After the attack in Krakow, authorities discovered the bodies of his family members in Ostrowiec.

Poland then observed two days of national mourning. Oksinski died of wounds sustained during his arrest at a local hospital on Monday.

Initial investigations have uncovered "very solid" evidence pointing to far-right radicalization and psychiatric issues as motives for the attacks, Zurek said.

However, Zurek and the centrist government of Prime Minister Donald Tusk has been accused by members of right-wing populist PiS party of lying about Oksinski's motives.