The Los Angeles County Medical Examiner tells ET that Benjamin's cause of death has been ruled a suicide by intraoral shotgun wound.
"Lisa Marie is completely heartbroken, inconsolable and beyond devastated but trying to stay strong for her 11-year-old twins and her oldest daughter, Riley," Presley's rep tells ET. "She adored that boy. He was the love of her life."
Unlike his sister, actress Riley Keough, Benjamin had stayed out of the public eye for the most part. However, last June, Benjamin made headlines as fans marveled at how much he resembled his grandfather, Elvis, in a family photo his mother shared.
"Mama Lion with cubs," Lisa Marie captioned the black-and-white photo, which showcases her wrapping her arms around Benjamin, Riley, and her youngest kids, twin daughters Finley and Harper.