Who?
He became the lead guitarist for KISS after Vinnie Vincent self-destructed himself out of the band after 1 album and 1 tour.
Mark St. John is one of the big unlucky bastards of the world... he recorded the ANIMALIZE album, and immediately got some for of arthritis that made him unable to play guitar. He attempted to tour in support of the ANIMALIZE album, but only did one full show before he had to quit.
So then he had a brain hemorrhage and died at the age of 51. Sheesh.