The police's southern district commander has choked back tears while answering pointed questions about whether officers could have prevented Edward Livingstone from killing his two children.
Livingstone threatened his former wife Katharine Webb, then shot dead Bradley, 9, and Ellen, 6, in January last year. He was found dead with his shotgun next to him.
The inquest into the deaths has ended, with District Commander Superintendent Andrew Coster saying he is sure the case will generate a lot of change.
Mr Coster told the inquest there were significant police failings in the Livingstone case, with mistakes in both record keeping and judgement made by a number of officers.
He said there were three main failings: police should have known of Livingstone's arson history; they should have paid more attention to the rape complaint made by his wife; and to the bullet shells that came home from school with the children.
However, Mr Coster said there was nothing in the four months leading up to the shooting that could have indicated what Livingstone was going to do.
He said domestic violence was the police's number one priority and he was sure this case would lead to a lot of changes.
The police have refused to talk further to Radio New Zealand, saying they won't comment till the coroner's findings are released.
The chief coroner, Judge Deborah Marshall, has reserved her findings after praising the children's mother for her quiet dignity throughout the hearing.