"He's had a brain bleed and is in a critical condition. He had some big hits and gave some big hits in the New Zealand teams champs last week in Palmerston North, but there was no indication of any concussion before Wanganui at the weekend.
"He is still in an induced coma so his brain can rest and get the time it needs to start to heal. We still don't know exactly how long it will be before they start to wake him, but the doctors will make that decision when he's more stable."
Heibner senior praised the superstock national officials, on-track paramedics and Wanganui and Wellington Hospital staff for their efforts.
"His mother Donna and I have been blown away by the amount of people sending messages of support ... and we would like to say thank you to them all."