His ex-girlfriend was at the party and she said they had an emotionally charged conversation.
She reported he appeared "upset and somewhat volatile".
Lawton-Karamaena left the party alone and told friends he was going "clubbing" in town.
He had asked a friend to accompany him but the friend did not have his ID so he stayed at the party.
Lawton-Karamaena was seen by three motorists on his way into town.
A bus driver saw him walking towards the bus. He said the teen gave him the single finger salute.
The next person to see him was a driver on Roberts Line who had to swerve and brake to avoid hitting him.
Then just before 2am, a truck driver saw Lawton-Karamaena sitting in the westbound lane of Napier Rd.
Moments later a driver heading west into Palmerston North saw the teen in the headlights.
He was walking towards town in the middle of the westbound lane.
The driver braked and swerved to avoid hitting him but the front left-hand side of the vehicle hit Lawton-Karamaena and he flew over the bonnet, landing on the road behind the car.
Lawton-Karamaena was then run over by two vehicles while he was lying unconscious in the middle of the westbound lane.
He died at the scene.
The coroner said she was not satisfied that Lawton-Karamaena's actions amounted to suicide.
"I consider Jarryn's death to have been the result of an accident, a tragic consequence of his alcohol-impaired judgment, and not a decision to take actions with the intention of ending his life."
