Jamie Ginns was on the police radar for assaulting the 20-year-old girl the night before he shot his partner, police said.

Only hours after being beaten and found tied on the Dalmeny St driveway, the victim told police a man called Jamie had raped and assaulted her.

The woman was in hospital when she told a police officer who was to blame and believes they could have prevented Ginns shooting Mata Glassie outside Tokoroa police station if they had acted more quickly.

"She shouldn't have been in that situation ... as soon as I got to the hospital I said his name straight away, 'Jamie, it was Jamie'." She couldn't remember his last name at the time.

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Police said the information provided was incomplete. They carried out a scene examination and interviewed witnesses, including the victim's boyfriend for two hours. By Friday evening they had enough information to consider Ginns as a person of interest.

Bay of Plenty District Commander superintendent Glenn Dunbier defended the police action.

"In any investigation, this one being no different, it is vital that police have solid evidence to arrest a potential offender to ensure that the information will stand up to scrutiny and in court."