Introduced as part of the second generation of the series Skins, James Cook was forever changed by what happened to him in season 4 and beyond. Known as one of the show's many troubled young characters, Cook was defined by his hard-partying lifestyle and general disregard for authority figures. Despite being somewhat of a troublemaker, Cook was usually gregarious and outgoing, but his temper was also volatile and unpredictable. Throughout seasons 3 and 4, Cook was seen to be quite impulsive with his decision-making, and that sometimes put him at odds with his closest friends.
https://screenrant.com/skins-what-happened-cook-season-4-killed-john-foster/