Sons of Anarchy has lost a member of its crew. Actor Alan O'Neill, who played the Irish mobster Hugh, has died at the age of 47, TMZ reports.

O'Neill was found by his girlfriend in their Los Angeles apartment on Wednesday night. No cause of death has been determined, but O'Neill had a history of heart issues, as well as problems with drugs and alcohol, according to TMZ.

The American actor was best known for his role in Seasons 6 and 7 of FX's hit Sons of Anarchy. His character Hugh was tied to Connor (Scott Anderson), who was brokering gun deals with SAMCRO. Though Sons of Anarchy's final season had a massive body count, Hugh made it out alive.

O'Neill also appeared in Undercovers and Tim and Eric's Bedtime Stories.