Police confirm that a male in black balaclava entered the Ashburton WINZ office this morning and has discharged a firearm.
As a result two people are deceased and a third person is in a serious but stable condition in hospital.
Police have named homeless man John Henry Tully as person of interest.
This is an ongoing situation and a full police response has been deployed.
Residents in the Ashburton area are asked to stay inside at this time.
The male left the scene on a push bike and should not be approached.
Police have no further comment at this time.
Anyone with information is asked to contact Christchurch police on (03) 363 7400.
Information can also be provided anonymously to the organisation Crimestoppers on 0800 555 111.