What killed mine worker Mustafa Sarı? Nature?

Mine worker Mustafa Sarı survived a mine accident four years ago. Eight of his colleagues died.

The other day, Sarı died at another mine accident in Gelik, in the Kilimli district of the Black Sea province of Zonguldak. 

What killed Mustafa Sarı? Did he die because of the "nature" of his job? 

His son Doğukan Sarı was interviewed and photographed four years ago, crying and waiting for his father at the entrance of the mine. They were also photographed later hugging each other. 

This time, Doğukan was filmed and interviewed at the morgue. When the microphone was held out to him, he told reporters the following:

 "Even though he survived that accident four years ago, my father was not hired by the Turkish Coal Institute [a state-run organization with better conditions] although they hired 12 other people. My father was an expert. He knew the mine business to the core. But they hired others who have no experience or knowledge. In the end, he had to take a job at less regulated mine. He went in alive but came out dead. He used to tell us there was water coming from the mine. I told him not to work in the mine but then I realized he had to work there to make a living. Even if I had told him so, he would not have listened to me. He was working in the mine for us, for the family." 

Was it "the nature of the job" that killed Mustafa Sarı?

Doğukan was trying to talk without crying. He is just 17 years old. 

"I will take care of my mother and my sister. I won't let them down. My father supported us and brought us up. He was close to retiring and had one more year to go. He always said, 'I can take an extra job after I retire.' But he wasn't able to retire. After the accident four years ago, he worked in...