My colleague has been following this story:

Their news release indicates the chemical was Hydrofluoric Acid (HF).

Google translates as follows:

Regarding the fatal accident involving a graduate student at our university
On the morning of 　August 27th (Thursday), an incident occurred in the Faculty of Science building at our university in which one graduate student was exposed to hydrofluoric acid. One graduate student and one undergraduate student who came to the rescue also sustained minor injuries and were transported to the hospital.

　Subsequently, the graduate student who was exposed to hydrofluoric acid was confirmed dead at the hospital to which he was transported. We offer our deepest condolences to the family of the deceased student and pray for his soul to rest in peace.

The two　students who sustained minor injuries are in good health.

　Our university takes this tragic accident, in which a precious student's life was lost, very seriously, at a university where educational and research activities should be conducted in a safe environment.

　We are currently investigating the cause of the accident in cooperation with relevant organizations. We take this matter very seriously and will strive to determine the cause of the accident. We will inform you again as soon as new facts come to light.

Hokkaido University , August 27 , 2026

Jeff