When the anger is intense, the person with Asperger's syndrome may be in a 'blind rage' and unable to see the signals indicating that it would be appropriate to stop. Feelings of anger can also be in response in situations where we would expect other emotions. I have noted that sadness may be expressed as anger.
Tony Attwood (2006). “The Complete Guide to Asperger's Syndrome”, p.143, Jessica Kingsley Publishers