A man has been charged with one count of a domestic violence-related assault occasioning actual bodily harm and one count of common assault and will face court today.
22-year-old Brandon Duncan, who was on parole, was arrested at Woy Woy Railway Station yesterday after a woman alerted police to concerns over a baby who was travelling with the man and a woman, who is believed to be the child’s mother.
Witnesses claimed the man hit the child multiple times with a mobile phone, allegedly dropped him on his head and repeatedly pricked him with a safety pin.
"It was hard to see it all happen," a witness, who did not wish to be identified, told 9NEWS. "It was horrible to actually see it all happen, and it was very, very upsetting."
The baby, who suffered injures to his head, is now in the care of Family and Community Services and is in a stable condition.
"One of the things we say in relation to domestic violence is - don't be a bystander," Police Superintendant Danny Sullivan told ABC. "Whilst looking at this terrible situation, one thing that we can draw from it is that bystanders on the train had the courage to intervene and had the wherewithal to contact police."
"I can only praise those bystanders for their quick thinking."