Dwayne "The Rock" Johnson says he's in pieces over his dad's death ... writing in an emotional goodbye letter to his father, "I wish I had one more shot to tell you, I love you."
Rocky "Soulman" Johnson died suddenly at 75 years old on Wednesday ... and in Dwayne's first public words since the tragic news, The Rock said he's broken up over it all.
"You were ripped away from me so fast without warning," he said. "Gone in an instant and no coming back. I'm in pain.