Earlier this week, police charged four men over the shooting.
A 41-year-old Nelson man has been charged with his murder. Three Dannevirke men aged 29, 35, 45 have been charged with being a party to murder.
"Whilst a link between Mr Whatuira's death and the suspected arson is not established at this time, police consider this to be a strong possibility," said Detective Sergeant Johnny Oram.
"We want to speak to anyone that has any information about this suspected arson, including reports of any suspicious behaviour witnessed in the area during the early hours of this morning.
Police and a fire investigator are currently examining the property.
Anyone with information is asked to contact Detective Sergeant Oram on 06-213 9613 or to call Crimestoppers anonymously on 0800 555 111.