Coroner Rachael Schmidt-McCleave said Ruatoto had been living in Northland at the time with his partner and three children.
He had recently moved back to live with his mother.
Ruatoto and two others had visited a property to smoke cannabis on the afternoon of July 9 before leaving.
The trio went and visited friends, travelling to an address on Te Tii Rd between 2.30am and 3am the next morning.
Coroner Schmidt-McCleave said police were unable to determine why the three men went to the Te Tii property, but suspected it was related to buying drugs, a debt owed or a planned confrontation with another man living at the address.
Shortly after they arrived, there was a fight between Ruatoto and a man at the property, Ash Rankin, the coroner said.
Ruatoto was tackled by Rankin, sending him falling into a glass sliding door.
He was injured, and driven to hospital by the two men he had spent the previous afternoon with.
“Medical staff immediately attended to Mr Ruatoto as he did not have a pulse,” Schmidt-McCleave said.
“CPR was commenced and Mr Ruatoto was subsequently resuscitated, and air lifted to Auckland Hospital.”
Staff at Auckland Hospital performed CPR once again, but Ruatoto had suffered cardiac arrest and could not be revived.
He was pronounced dead just before 10am.
An autopsy found the cause of his death was penetrating, sharp force injuries to the medial left arm near his elbow.
Methamphetamine and cannabis were also found in his blood.
Forensic pathologist Dr Charley Glenn concluded Ruatoto’s injuries were “very consistent with an accidental fall into a glass door”.
Police investigated Ruatoto’s death, determining Rankin was not criminally liable for what happened.
They said Rankin had acted in self-defence.
“Police found there was no evidence to suggest Mr Rankin intentionally acted to cause harm to Mr Ruatoto, or that the incident was premeditated,” the coroner said.
“I am satisfied that the evidence before me establishes that Mr Ruatoto was involved in an altercation with Mr Rankin, which resulted in Mr Ruatoto accidentally falling through a glass sliding door and sustaining a fatal injury to his arm.”