Registrar Martin Kane refused to release the man back into the community during his initial bail application made last week, citing serious concerns for the safety and welfare of his young family in the wake of the alarming allegations.

Documents tendered to the court said the man, who cannot be named in order to protect the identity of his son, was at his parents' house with his girlfriend and their child on March 3 when they began arguing about her alleged infidelity.

Police will allege the 20-year-old hit his girlfriend repeatedly in the head while she was holding the baby.

He then took the child out of her arms and put him on a play-mat, before allegedly continuing his assault of his young partner by dragging her onto the floor and punching her multiple times.

Police will allege the entire incident was captured on CCTV cameras installed inside the home.

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The woman sent her mother a text message asking her to call police, however was able to convince her boyfriend to let her and the baby leave the house in the meantime.

It is alleged the man buckled the child into the baby seat before grabbing hold of his partner and saying "I will kill the three of us".

She told police she managed to calm her partner down and agreed to drive him to another house nearby.

She dropped him off then made her way to a friend's house, where she spoke with police and showed them the CCTV footage, which she had access to on her phone.

The man tried to contact his girlfriend several times while she was speaking with police, telling her he was sorry. He was arrested later that afternoon and charged with assault and breach AVO offences.

He told officers he'd taken an overdose of pain medication and had planned on ending his life, prompting police to take him to Shellharbour Hospital for a mental health assessment.

He later told doctors he had no intentions of harming himself and was released back into police custody.

The man's lawyer told police last week that her client admitted hitting the victim with an "open hand slap" but denied punching her or threatening her.

She claimed the physical injuries police observed on the woman - a small amount of bruising and some scratches - was not consistent with claims she was repeatedly punched.

If you or anyone you know needs help, call Lifeline on 13 11 14; Kids Helpline on 1800 551 800; or Beyond Blue on 1300 224 636.