Wellington police have confirmed they have referred the death of a man questioned during a homicide investigation to the Independent Police Conduct Authority.
Timothy Parlane was interviewed by the police on 4 March about the stabbing of Johnsonville man Matthew Hall.
Matthew Hall died as a result of what police describe as a ferocious attack while asleep at his Johnsonville home. His body was discovered on 15 February.
Police say Mr Parlane, who was a person of interest in the case, died on 5 March when hit by a train.
Detective Senior Sergeant Dave Thornton says it is standard procedure to refer the death of a person who has been dealing with police to the IPCA.
Inquiries also underway by the Coroner.
Police still want to hear from woman
Meanwhile, Detective Senior Sergeant Thornton says police still want to hear from a woman they believe visited Mr Parlane the day before Matthew Hall's body was discovered.
Another woman who has spoken to police about Mr Parlane has provided information that has become a major part of the inquiry.
Detective Senior Sergeant Thornton says police are still looking for sightings of Mr Parlane's vehicle, Nissan Primera. His cellphone and shoulder bag are also still missing.
Both Mr Parlane and Mr Hall, who was a mental health worker, were active in the death-metal music scene in Wellington.