Addressing this problem at 1 year of age will require a lot of patience and consistency. Basically what has to happen is for you to teach him that the person is not a threat. As an example if someone approaches you would need to greet them and interact with them while you have him controlled in your arms. The person should interact with you, talk calmly to him but not make reach for him or use hand jesters. You may need to go through this scenario for weeks and with different people. If you can provide a description of the circumstances leading up to his aggression I might be able to advise you better.