Managing Director Rod Petrie said on the club's official website:
" Everyone at the Club was stunned and saddened to hear of the death of Liam O'Sullivan at just 20 years of age. While we all feel a sense of loss, our thoughts and sympathies must go out to his family.
" Liam had begun to battle back to fitness following a long period of injury, and had shown great character in doing so."
" He was working with both the Club and his family to overcome his injury and some personal issues, and everyone who worked with him is devastated at his untimely death."
Liam's dad, Des added " Liam had struggled hard to come to terms with, and then overcome his injury, so this has come as a terrible shock. We are all stunned - he seemed to be getting on well."
Our thoughts and prayers go out to the O'Sullivan family at this tragic time.