"We are deeply shocked and saddened to learn of the sudden passing of our client and friend Karl Shiels, yesterday," the actor's agent, Lisa Richard, said in a statement to Raidió Teilifís Éireann (RTÉ).
"Karl was a uniquely talented individual, simultaneously intense, light-hearted, funny, sharp-witted, outspoken and intensely powerful as an actor, director and artistic director of the Theatre Upstairs - where he was such a support and mentor for young writers, actors and directors - and of his own company Semper Fi before that.
"Karl was a remarkable force in Irish theatre and hugely loved and respected by all who worked with him.
"Our hearts are broken but today our thoughts are with his partner Laura and his family, his children and their mother Dearbhla and his many close friends among whom we count ourselves lucky to have been for so many years."
"Joining Fair City in 2014, Karl Shiels made his mark immediately playing the formidable Robbie Quinn, and always brought such, warmth, talent and humour to Carrigstown," de Courcy said. "We are absolutely devastated and he will be so greatly missed by the entire cast and crew. Our thoughts are with his family at this incredibly sad time."
Shiels earned his first acting credit in 1999 (the same year he won Best Actor at the Dubin Theatre Festival for his role in Comedians) in the short Between Dreams, going on to appear in a number of projects, like Peaky Blinders, Foyle's War and The Tudors. He joined the cast of Fair City in 2014 and was involved in a number of high profile storylines. In Batman Begins, he played a thug imprisoned in the Arkham Asylum.0comments
In 2010, Shiels appeared in the award-winning play Penelope. That same year and the year after, he was nominated for Best Actor at the Stage Awards and the Irish Times Theatre Awards, respectively.
His extensive work at the Abbey Theatre included Beauty in a Broken Place, At Swim-Two Birds, The Barbaric Comedies and Henry IV (Part One). Other theater work included The Shadow of a Gunman, The Spanish Tragedy, The Duchess of Malfi, This Lime Tree Bower and the acclaimed Howie the Rookie.