Robert Yancy, a musician who was the only son of the iconic singer Natalie Cole and the grandson of the jazz legend Nat “King” Cole, died Monday, Aug. 14, 2017, of a heart attack, according to multiple news sources, including The Associated Press. He was 39.

Yancy was found dead by a friend at Yancy’s apartment in California’s San Fernando Valley, according to TMZ.

Police listed his cause of death as natural causes pending results of an autopsy and toxicology tests. Drugs were not involved in the musician’s death.

“We are just numb,” Yancy’s aunt, Timolin Cole Augustus told The Associated Press. “The only consolation is that he’s with the person he loved the most.”

Yancy, whose father, music producer Marvin Yancy, was the first of Natalie Cole’s three husbands, died less than two years after his mother died of congestive heart failure Dec. 31, 2015, at 65. Marvin Yancy died March 22, 1985, also of a heart attack, at 34.

Robert Adam “Robbie” Yancy was born Oct. 14, 1977. A drummer, he frequently toured with his mother (pictured, above, with her son). He also performed at his mother’s funeral in January 2016.

At the time of his death, he was working in the music industry.