Schrodinger's Bane

Schrodinger's a circle of squad. A almost perfect squad who met each other only through internet about years ago. They are living in one roof, with no issues or problems regarding each other. Despite of their differences, still, they can manage to have strong and countable bond. They have been through ups and downs as years goes by, but then when they though they already live the life they seek since they day one, a big obstacle in their lives will occur. Death occured unforeseen, and by that, the greatest mystery of their lives began. Who's the reason behind mysterious death?