I could very well be autism that is causing this behavior. How long has his behavior been aggressive?
Has he been evaluated by a child psychologist? I'd suggest letting his team of teacher's and therapists (OT, PT, whoever else is invloved) know of the fecal smearing and aggression - they know him and may have some insight as to why this is occuring.
But do have him evaluated for this aggression- it may be that he needs to start counseling or even a mood stabilizer to be able to function more appropriately.