The woman, also aged 19, said she was woken by police at 8.25am.
Until then, she had not realised he had left their Mornington home.
Her husband had requested she and their 2-year-old daughter be moved to a "safe house", she said.
Police moved the family to another location at 9am.
The man's wife contacted the Otago Daily Times, frustrated police would not let her attempt to talk her husband down from the ninth floor of the building.
He had phoned her shortly before noon and said he would give himself up if she came to the scene, but the police officer stationed with her would not let her, she said.
Inspector Alastair Dickie said involving family members in negotiations was a last resort and police followed the correct procedure when dealing with an armed person.
The woman said her husband had a history of psychiatric episodes.
She and her family had tried but failed to get him help from various agencies after he had a psychiatric episode last October, she said.
"He just needs help, but no-one will listen."
The man lost his factory job as a result of the episode, she said.
The man talked to his wife and the police using a cellphone during the stand-off.
The woman said they met when they attended a course in 2004.
She described him as a "good husband and a wonderful father".
