A couple possible answers to this. My opinon its one of two things. A.) and most likely answer since hes being trained by Flex like Big04 said, this is synthol. Its not just the fact that he blew up, but his lats arent as symmetrical as they were before...... commonly this happens with synthol if it doesnt really spread out good enough.
B.) He has just now started super high doses of HGH. HGH at high doses 10iu's and up are what give guys the freak factor and thats what makes them freaky huge. Yeah of course hes "juicing" hardcore, but chances are thats not much of factor since hes really advanced, the HGH would be more important for extra growth in his stage.