Hello, and thank you for requesting my help. I appreciate it.
I agree, the fact that he has warned you that he is not a good person says a lot. No one starts a relationship by saying something like that without there being a significant issue behind it, whether that is a need for attention (a statement like that could make you interested in finding out what the person meant by that which equals instant attention), or it could be that the person finds it fun to set you off guard. It is unlikely that there is a good reason since someone who is insightful enough to know they have issues would most likely be interested in addressing those issue for fear of being rejected by potential partners.
Also, if he has hurt other partners in the past, that is also a warning sign. What you don't want to see is a string of hurt partners that have a very poor opinion of this man.
It is unlikely that a traumatic event in his present life, such as his son's death, caused him to act as he does towards others. He may outright reject others in fear of getting close and therefore getting hurt by a loss, but being directly mean by ignoring someone in public usually indicates hostility and self importance. And those traits are attributed usually to a personality disorder, which develops when the person was a child, usually through abuse or trauma of some sort.
It is difficult to tell without seeing him face to face exactly what disorder he might have. But I can provide you with links that I find helpful that describe narcissism and other personality disorders so you can see which symptoms he has:http://www.nmha.org/go/information/get-info/personality-disorders http://psychology.about.com/od/personalitydisorders/a/personalitydis.htm http://psychcentral.com/disorders/sx36.htm
The most important part of the situation is how you feel. If you are finding yourself feeling hurt, on guard, questioning yourself or experiencing low self esteem, you may be dealing with someone with a personality disorder. And questions this early in the relationship are also an indication that something might be wrong. You are picking up on something and even if you cannot put your finger on it yet, your insight and perception are trying to tell you something. So it may be ok to take a step back and be cautious. Until you know more, you may want to keep yourself open to other relationships and let this one take a back seat for a while.