Nick Nordella plays "young man" in episode 7(great red dragon) and 8(Red John) (imdb casting: http://www.imdb.com/title/tt3196216/?ref_=nm_flmg_act_2
http://www.imdb.com/title/tt3196212/?ref_=nm_flmg_act_2 )

Here's a clear shot of his face: https://si0.twimg.com/profile_images/378800000505333291/e2dd7cd4a86c764cf6895d619e1a6752.jpeg

Now here's a clear shot of xander berkeley(he who plays mcallister): http://images2.wikia.nocookie.net/__cb20120918094811/marvelmovies/images/2/2b/Xander_Berkeley.jpg

The "young man" role is probably a flashback of his visualize experience and first murder!!
They looks almost the same, a young to old comparision.
Look familiar? yeah i thought so too, discuss =D