A car pulled up behind him and the back passenger yelled out "oi".
As he turned around, he caught a glimpse of the beer bottle hurtling towards this head.
The force knocked him to the ground where he face-planted on the broken bottle.
The glass caused lacerations on his face. He was diagnosed with a light concussion.
Tiaan said he still feels safe on the streets of Havelock North but doesn't want it happening to anyone else.
He is "really keen" for the perpetrators to be brought to justice.
"I hope they are caught and at least spend a period behind bars. Hopefully someone saw something."
Tiaan is slowly recovering from the incident and hopes to return to the rugby field when the holidays are over.
"I'm feeling a bit better, I've had a few headaches.
The doctor said it would be about 10 days until I stopped feeling the effects," Tiaan said.
Tiaan sought help from people at a nearby cafe for his injuries.
He is very grateful for the response by staff at the nearby Barm Bracks Cafe.
"They cleaned my face and made sure I got home safe," he said.
His father is furious about the incident.
"To attack someone like that while they are innocently walking to school is ridiculous," Mr Jarman said.
"He is very bemused and angry about why someone would do this."
Police want to identify the red vehicle that was involved and the car's three occupants.
The driver is described as a Maori of medium build, the front seat passenger as male Caucasian and the rear seat passenger as a skinny male Maori in his 20s.
Anyone with information about the incident should contact Detective Glen Restieaux at HB Police on 06 8310700 or information can be left anonymously on Crimestoppers 0800 555 111.