NSW good Samaritans caught up in assault

Two good Samaritans have become witness to a violent confrontation after trying to help a man in Sydney's west.

The man and woman came across the 51-year-old lying on the ground at a bus stop in Liverpool about 2pm on Friday but he became aggressive when they tried to wake him to check on his welfare, police say.

They say another man who fled the scene and remains on the run set upon the man, punching and kicking him.