"When I heard, I immediately flew back to California, and went directly from the plane to his mother's house," Diesel said in a post. "I thought they needed my strength, but realized when I got there and broke down before his family, that it was I who needed theirs."
"His mother hugged me and said I am so sorry... I said sorry? You're the mother who lost a son?... She said yes, but you lost your other half...," Diesel added.
Diesel previously stopped by Walker's crash side in Valencia, Calif., for an impromptu visit with mourners.
"If he could see for himself that all of you have showed up to show my brother love at this hard time, and the family gets to see all of you show the love that you've shown Paul, it's going to stay with me forever," Diesel said over a police officer's loudspeaker.
"I just wanted to say thank you. Thank you for coming down here and showing that angel up in heaven how much you appreciated him," he said.