Four teenagers are part of a group of six who were arrested after a brawl in front of an innocent family’s home in Sydney.

A 35-year-old man was allegedly hit in the head with a hammer and was left unconscious on the front lawn of the house.

He sustained a serious head injury and is in a stable condition in hospital; a 15-year-old boy was also taken to hospital, but has since been released.

The brawl began when one group began smashing a car sitting in the driveway of a house in Ruse, near Campbelltown, on Saturday afternoon.

Then the two groups clashed with the men and teens holding weapons such as metal poles. A children’s bike was allegedly used as a projectile.

At one point, one of the teens tried to retreat to a nearby house but was not let in by the owner.

Courtney, the resident whose house became the scene of the violence, was stunned and shocked by what occurred.

She watched the brawl occur from her living room.

There was a man injured here next to my car,” she told 9News.

“They damaged the front of my house, my car, everything.”

Police believe the brawl began due to an argument at a nearby shopping centre and are unsure if the two groups are known to each other.