Johnson was in Las Vegas shooting his HBO series, Ballers, when he got the news, a source tells ET, adding that the action star immediately jumped on a plane to be by Lauren's side.
The father of two later took to Instagram to pay tribute to Sib, who was the drummer for the band Boston, calling him his "second dad."
"Rest In Peace & Love to my second dad Sib Hashian," Johnson began his touching post. "Don't know why things have to happen the way they do sometimes. When loved ones leave us so suddenly without having a chance to say goodbye. Perhaps the lesson here is the reminder to live our lives as full and as present as we possibly can, because we just never know what's around the corner."
"What a full and exciting life this man lived. What an amazing family he created, loved, watched over and protected," he continued. "Being on stage, in front of adoring fans, friends and family. Keeping the beat one last time. Your passing in this manner is extremely poetic and somehow beautiful."