The Oak Ridge Boys are mourning the loss of one of their own. Billy R. Smith, Jr., their longtime bus driver, passed away unexpectedly on Sunday (Sept. 21).

The Grand Ole Opry members also took to Facebook to express their sorrow.

"Our hearts are saddened over the sudden loss of our long time bus driver Billy Smith!!" they shared on the band's Facebook page. "RIP Bill EEE We all love you brother... Until the day."

Smith retired from the road last month, after more than 11 years of traveling with the Oak Ridge Boys. His brother, Randy, was a member of Lee Ann Womack's band for several years.

Funeral services are pending. The Boot extends our deepest condolences to his family.