The news was shared by his daughter, Elizabeth Dennehy, who confirmed that he died of natural causes unrelated to COVID-19:
It is with heavy hearts we announce that our father, Brian passed away last night from natural causes, not Covid-related. Larger than life, generous to a fault, a proud and devoted father and grandfather, he will be missed by his wife Jennifer, family and many friends. pic.twitter.com/ILyrGpLnc3— Elizabeth Dennehy (@dennehyeliza) April 16, 2020
Dennehy won Tony Awards for his roles in Death of a Salesman (1999) and Long Day's Journey Into Night (2003). In addition to his onstage work, he also had memorable roles in First Blood, Cocoon, Tommy Boy and Presumed Innocent, as well as recent TV shows like Hap and Leonard and The Blacklist.
Dennehy is survived by his second wife Jennifer and his children Elizabeth, Kathleen, Dierdre, Cormac and Sarah.