A father and two of his three children have been killed in a horrific smash as they waited for a school bus in regional NSW on Tuesday morning.

Police believe Shaun Zagar, 28, his eldest son Kaleb and daughter Zara were sitting in their parked blue Mazda sedan about 8.10am on Tuesday when they were struck by a green Mitsubishi Magna on McDonalds Bridge Road, Dyraaba, about 15 kilometres north-west of Casino.

Shaun Zagar: Killed while waiting in his car with his children.

Inspector Mick Dempsey from Lismore police said: "For some unknown reason the green Magna crossed on to the incorrect side of the road way and struck the near side of the blue Mazda."

The trio were thrown from their car on impact and were dead when police arrived a short time later.