Masiak, 31, founder and editor of the independent news website Nasza Mława, died from a brain injury after being assaulted at a bowling club in the city of Mława, central Poland, at about 2 a.m. on June 14, 2015, according to local press reports. The journalist, who also wrote for the Nasza Mława website, was followed into the club's bathroom and assaulted, according to news reports that cited details from CCTV footage.
Masiak reported on illegal drugs, environmental pollution from chicken farms, arbitrary arrests, and crime for Nasza Mława. He also reported on local mixed martial arts competitors, according to local press reports.
A day after Masiak died, police issued an arrest warrant for Bartosz Nowicki, a martial arts instructor, who they said was suspected of attacking Masiak, according to reports. Authorities detained two other men in connection to the killing but released them shortly after taking statements, news reports said. CPJ could not determine if the men had been charged.
In statements to the press on June 15, 2015, police said that the killing was the result of a quarrel between Masiak and Nowicki, allegedly over a woman. Later, investigators announced that they were looking at all possible motives, news reports said.
In a letter sent in July 2015 to the Council of Europe, Polish authorities acknowledged that Masiak was a journalist, but said their investigation had not found links between the attack and his journalism. They said a district court had issued a European arrest warrant on June 25, 2015.
Masiak had been assaulted and threatened before, moves he said were in retaliation for his journalism. In January 2014, Masiak was attacked in front of his apartment building, according to Index on Censorship, the U.K.-based press freedom organization. Speaking to regional radio station Polskie Radio at the time, Masiak said he was sprayed with a gas, then kicked and beaten by a masked attacker who did not speak during the assault. In the radio interview Masiak said he did not believe it was a robbery because neither his camera nor his cell phone, which he had with him, were taken. According to a translated version of the interview, Masiak said: "It was certainly about content published on [Nasza Mława.] I see no other possibility. I can guess which content and I have an idea who stood behind the attack, but I cannot reveal this. I leave that to the police."
In December 2014, a fake obituary notice was delivered to the house of the journalist's mother, according to Index on Censorship and local news reports. The journalist reported both incidents to the police, saying it was a retaliation for his journalism, Index on Censorship and local reports said. No arrests have been made and investigators have not identified the person behind the threat, according to Index on Censorship.
A local journalist, who worked with Masiak on Nasza Mława, told CPJ Masiak had been concerned for his safety and recorded all of his telephone conversations.
Katarzyna Kozłowska, of Radio dla Ciebie, who knew Masiak, told Gazeta Wyborcza in June 2015 "[Masiak] told us that he was afraid for himself and his family."
On October 30, Nasza Mława reported that the prosecutor’s office said it had completed an analysis of the journalist's telephone billing records but that it did not reveal any results.
In April 2017, the Płock District Court convicted Nowicki of “causing serious damage to health, which resulted in the death of the injured party,” and sentenced him to seven years in prison, according to news reports.
In October 2017, the Łódź Court of Appeal upheld the sentence, according to local reports.
The journalist’s family said that they would like the case revisited, according to a report published the same month as the appeal.
A person following the case closely, who asked not to be named for security reasons, told CPJ in August 2019 that they disputed the court's findings that the killing was the result of a personal dispute.