I am a mother to a 3 yr old boy. His aggressive behavior is becoming a major source of concern for me. He is always hitting, pinching or pulling hair. He does it to complete strangers, friends, relatives and even me. I have tried everything, explaining, giving time outs, scolding, rewarding; but nothing has seemed to work. There are times when he behaves like an angel but the very next minute he is hitting someone. Please help.