Emergency services were called to the scene near Timaru after a station wagon and a truck collided on State Highway 1 near Brosnan Rd about 5.10pm on November 20.
Ivar Crowther, 5, and his father, Steven, died after a crash.
Police said the white truck was heading south, while the silver station wagon was heading north.
Ivar’s mother Hana Kroon has posted to social media about losing her son.
"Our hearts are broken in a way we never knew was possible, and we are still trying to understand how life can change so painfully and so quickly,” the post read.
"His smile could brighten any room, always the one to give the hugs, and his little spirit was full of kindness, curiosity and love.
"No words can explain the pain of losing him, or the emptiness that now sits where his laughter used to be.
"But I am so grateful for the five precious years we had with him – years filled with memories I will carry close to my heart forever.
"Rest gently, my sweet baby boy. You will be forever loved, forever missed, forever five and forever ours."
"Your messages, visits, hugs, meals, donations and every small act of kindness have not gone unnoticed and has helped us hold up during the most painful time of our lives,” the post read.
"No words can fully express how much your support has meant, but please know that we are truly grateful.
"Your love has helped us keep going when everything feels impossible.
"Now I have to learn to navigate a life without my baby boy and it is going to be the hardest thing I will ever have to do.
"Thank you for honouring Ivar, for speaking his name, and for wrapping us in so much care.”
Ivar’s School, Sacred Heart, said in a newsletter: "Our thoughts and prayers remain fully with the Kroon and Crowther whānau in what is an impossibly sad situation."
-Allied Media
