Boothe, best known for his powerhouse performances in westerns like Tombstone
and the HBO original series Deadwood,
died of natural causes in his sleep Sunday morning, the actor's rep confirmed to ET.
Boothe's death was first announced on Twitter by his friend and colleague, Beau Bridges, who wrote, "It's with great sadness that I mourn the passing of my friend Powers Boothe. A dear friend, great actor, devoted father & husband."
The actor made his film debut in the 1977 film The Goodbye Girl, and built a career on playing mainly darker, villainous roles. Recently, he starred as the sinister Senator Roark in 2005's Sin City and its sequel, Sin City: A Dame to Kill For, in 2014.
Boothe also worked extensively on a number of TV shows, including Philip Marlow, Private Eye in the 1980s and the political thriller 24. Most recently, he had a recurring role on Nashville playing Lamar Wyatt, and appeared in several episodes of Agents of S.H.I.E.L.D. as Gideon Malick.
The celebrated actor won an Emmy in 1980 for starring as Jim Jones in the TV miniseries Guyana Tragedy: The Story of Jim Jones
. He was also nominated for a SAG Award for playing Cy Tolliver on Deadwood.
He is survived by his wife, Pam, daughter Parisse and son Preston.
Boothe's rep told ET, "There will be a private service held in Texas where he was from. A memorial celebration in his honor is being considered for a future date. Donations can be made to the Gary Sinise Foundation, which honors the nation’s defenders, veterans, first responders, their families and those in need."