"Everything indicates that this brawl was not the result of an ethnic conflict. It was linked to alcohol and some kind of personal dispute," Tusk told reporters in parliament on Friday.
The attack took place on 9 July, when a 36-year-old Polish man and his 44-year-old partner were beaten by three Ukrainian men, aged 28, 30 and 37, all reportedly under the influence of alcohol.
The victim died in hospital on 11 July from his injuries; the woman did not require hospitalisation.
The suspects, who had earlier been drinking with the couple, deny the charges against them, which are being investigated by prosecutors in Bytów.
The Polish PM said any act of violence was a serious crime "regardless of who commits it."
"For me, it does not matter who is doing the beating, it does not matter who is showing contempt for others, whether they are Ukrainian or Polish. If someone does something like that, they should face criminal responsibility," Tusk said.
He warned against a slide into "contempt, hatred and hate" towards people of different views or nationalities, which he said would be "hell."
Tusk also referenced concerning rhetoric from opposition figures over the case, naming far-right party leader Grzegorz Braun.
He added that he had also observed "dangerous tendencies" across the border in Ukraine, saying it was the responsibility of politicians in both Kyiv and Warsaw to prevent tensions escalating between the two nations.
Ukraine's ambassador to Poland, Vasyl Bodnar, condemned the killing on social media, saying there could be "no justification for such brutal acts in a civilised society."
Ukraine's consulate in Gdańsk said it was "shocked" by the attack and expressed condolences to the victim's family, adding that it had full confidence in the Polish justice system.
It stressed that "crimes have no nationality," urging mutual respect between communities.
The case comes against a backdrop of rising anti-Ukrainian sentiment in Poland.
(ał)
Source: PAP