Brandon Blackstock's "soulmate" Brittney Marie Jones, identified in Blackstock's obituary as his "loving partner in life and business," previously worked as Kelly Clarkson's production assistant.

Brandon Blackstock, ex-husband of music star Kelly Clarkson, died last Thursday, August 7. An official cause of death for the 48-year-old has been confirmed. Silver Bow County Coroner Dan Hollis told PEOPLE Monday that Blackstock died of melanoma,

Blackstock’s ex-wife Clarkson—who shared daughter River, 11, and son Remington, 9, with the late talent manager—and his stepmom McEntire are reportedly “devastated” by Blackstock’s death on August 7, which comes after a three-year cancer battle.