Basurto Hospital has confirmed the death of Athletic Bilbao fan Inigo Cabacas Liceranzu from injuries sustained after last week's Europa League game against Schalke.
The 28-year-old had been in a coma because of a head wound he suffered following the second-leg encounter at San Mames.
After being removed from sedation on Monday, it was discovered that Liceranzu was displaying no signs of brain activity and the decision was taken by his family to take him off life support.
It has not yet been established how the Athletic fan suffered the injuries which claimed his life.
According to El Pais, family members and friends have claimed that Liceranzu was shot in the head with a rubber bullet by riot police, who were trying to quell violent clashes in the city centre after the 2-2 draw.
An enquiry has been launched into the incident and police sources have reportedly claimed that the cause of death will only be known after an autopsy.
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