UPDATED 5:15pm: Police have told the media to refer to the Ashburton gunman suspect as Russell John Tully.
They say there's a man in Christchurch called John Tully and they don't want the two to be confused.
Russell John Tully goes by the name John.
Police say they've flooded Ashburton and surrounding areas as they hunt for Mr Tully over a fatal shooting at the local Work and Income office.
Canterbury District Commander Superintendent Gary Knowles says 100 staff members are working on the inquiry.
He's asking people living in the Lake Hood area and south east Tindall to keep an out eye overnight.
Superintendent Knowles says those residents should report anything suspicious immediately and also lock all their out buildings are locked.
He says they won't stop the hunt until the find Tully - with patrols to take place right through the night.
Earlier, the Ministry of Social Development has confirmed the two people shot dead at its Ashburton Work and Income office were staff members.
Chief executive Brendan Boyle says they are all devastated by the death of two colleagues.
He says their thoughts and prayers are with a third staff member who is in a critical condition in hospital.
Police name man of interest after fatal shooting
Police have named the man they are looking for after two people were killed at Ashburton's Work and Income this morning.
He is Russell John Tully.
A press conference was held by Superintendent Gary Knowles.
He says Tully is dressed in camouflage clothing and may be carrying a sawn-off shotgun.
Superintendent Knowles says they are asking for Mr Tully to come forward
"He at this stage is only a person of interest and we would like to speak to Mr Tully. We believe he is somewhere in the greater Ashburton area and we would like him to come forward and liaise with my team.
"He is a person of about 48 years of age. Medium height 183(cm) and solid build. We believe that he may have a shaved head."
He says it's not a case of a lock-down but people need to be prudent
"If they see anything suspicious, anyone in their backyards, anyone hiding in a shed, anyone of interest please contact us urgently. We want to find this guy."
A third person is in a serious but stable condition in hospital.
A second cordon was set up down by Ashburton River and armed police ran down the riverbank about 11:30am.
Police have advised locals living close to the river to stay inside as they hunt for John Tully.
Wayne Williams received a knock on the door from police late this morning, advising him they were looking for a gunman.
"Sitting there watching TV and then you hear the helicopter come and get refuelled but it's been circling around here for the last hour or so. So I'm assuming that he's not far away from here."
Mr Williams hopes police have some success by the time it gets dark.
A mobile command unit has been set up.
Newstalk ZB's Tyler Adams was on the scene.
"I'm looking at three armed police at the moment. They've blocked off two square blocks of the inner city where this incident unfolded. At the moment they're still patrolling the outskirts of these blocks.
"It is not known at the moment what has happened to this gunman, whether as we know at this stage it appears he's still on the loose, whether they have cornered him in these two separate blocks it is unknown at that stage but it certainly seems to be the case, with every police officer that I can see armed."
Police scene outside Ashburton WINZ office
Residents in Ashburton are asked to stay indoors while the situation is still ongoing.
A man entered the office just after 10am and fired a gun, police said.
The man, who was reportedly wearing a balaclava and carrying a shotgun, left on a bike afterwards and was this morning still on the loose.
Schools and early childhood centres are keeping children inside until further notice.
The Ministry of Education says it's contacted all schools in the area and they have been prompt in keeping children safe.
A hockey tournament at Ashburton College has been cancelled.
Armed Offenders Squad (AOS) officers from Christchurch were sent to the scene, police confirmed.
A witness who was in the building at the time said a man wearing a black balaclava entered and shot two women, one of whom was interviewing him at the time.
He believed they were both WINZ staff members.
"It was incredibly loud, I could feel the air whoosh past my head," he said.
He followed the man outside.
"He must have broken the gun down because he put it in his back pack," the witness said.
Two other people who had just left the WINZ building saw a man wearing a balaclava and carrying a shotgun enter the premises.
Soon after they heard two shots.
A woman, also believed to be a staff member ran out and shouted at them to call the police, before running into the nearby medical centre.
They said the man's bike had been chained up on a street corner.
He headed east on Moore Street, leaving his bike helmet on the street.
A postie at a business across the road heard the man screaming and swearing as he left the building.
A staff member at an automotive garage across the road from the Work and Income office said she wasn't aware of any incident until she went outside for morning tea break and saw a cordon around the building.
"There were a couple of ambos and police there with a big cordon but other than that we didn't know it had happened."
Suspect had been offered emergency accommodation
The main suspect in the Ashburton Work and Income shooting had previously been granted emergency accommodation.
Police have named 48-year-old John Tully as the person responsible for killing two people and leaving another in a serious condition, after the shooting at the town's Work and Income office.
Ashburton Mayor Angus McKay says he has met the man during his search for temporary housing with Presbyterian Support.
"Presbyterian support looked after him very well. The support normally is for one or two nights. I know this gentleman was four. So everything has been done in the past for this gentleman."
Mr McKay says Tully was never violent or aggressive in any of his dealings with him.
Mr McKay says it's a very close knit community.
"And we're only dreading when the names are announced from Work and Income whether they were staff or whether they were customers, no one knows yet. So when those names are released this town will probably go into shock."
Peters unaware of suspect's letter
Winston Peters is unaware of a letter sent to him by the man accused of shooting two people dead at Ashburton's Work and Income this morning.
John Tully is believed to have sent a letter to the New Zealand First leader a couple of weeks ago in an act of desperation to find housing.
Mr Peters says he's been too busy to read the letter.
"I would expect my staff would have written back to home, but I haven't a chance to attend to it. I've been on the road."
Mr Peters says today's shooting is tragic and certainly not something you'd expect to happen in New Zealand.
New Zealand First says Mr Tully wrote to them on August 14, saying his local MP - National's Jo Goodhew - had failed to give him any help.
The party would not release the email, but said it was also sent to National's Gerry Brownlee, Paula Bennett and David Carter.
However, it's understood the other email addresses were incorrect, and the National MPs did not receive the email.
Jo Goodhew says Mr Tully contacted her electorate office.
"I haven't met him myself but certainly he had made contact with my office."
It's not yet clear what response, if any, Mr Tully received.
Ministry of Social Development quick to act
All Ministry of Social Development offices in Ashburton, Timaru and Christchurch are closed following the shooting.
Chief executive Brendan Boyle says they are all shocked by the news of this morning's incident.
He says they will be there for their colleagues to support them as they come to terms with what has happened.
Mr Boyle says the police are handling this serious situation.
He says the offices will remain closed until more is known.
And Social Development Minister Paula Bennett is on her way to Ashburton.
It is not known when she will arrive.
Ms Bennett says a lot of the details are still hazy.
"An absolute tragedy and it's kind of hard to put words around it to be honest, so I'm heading to Christchurch and we'll wait there."
There's no clue yet as to what motivated the shooting.
Ms Bennett says the most important thing is for locals to stay safe.
"The perpetrator is still on the run so my advice is certainly to follow police instructions and let them do their job at this time."
Ms Bennett says the shooter is still on the loose, so locals should stay indoors and follow all police instructions.
Police Minister Anne Tolley says she is receiving regular updates from the police commissioner on the situation.
PSA offers its support
Workers at the Ashburton Work and Income office are being supported by the Public Service Association.
Two people are dead, and one a serious but stable condition in hospital after a shooting at the office this morning.
PSA National president Richard Wagstaff says they've already sent staff to Ashburton to offer assistance.
"It will certainly mean that there's counselling that will mean that they get space away from work to be able to recover as best they can."
Mr Wagstaff says it's a tragedy that two people left for work this morning and won't be returning tonight.
Fatal shooting sends shock through community
Rangitata MP Jo Goodhew says the fatal shooting has sent shock through the community.
"I think it's out of the ordinary for it to happen anywhere in New Zealand but when it happens so close to home or at home so to speak it just hits even harder."
Ms Goodhew says her heart goes out to those who knew the people killed.
She says they're also fearful as police continue to search for John Tully.
"We need to stay strong for each other because boy we need it right now."
Key cancels policy announcement
John Key has cancelled plans to announce National's tax cut policy - and is offering condolences to the families of the victims of today's Ashburton shooting.
The suspect, John Tully, remains at large, after two people were killed and another seriously injured at a Work and Income office.
Mr Key has just held a media conference at parliament.
"Like all New Zealanders, I am shocked and deeply disturbed by what has happened today. My sincere condolences go to the families of those killed and injured. I know police are working extremely hard to bring the person responsible to justice."
He wouldn't be drawn on speculation the suspected gunman - John Tully - was a homeless man who was struggling to try and get housing.
"They've got some initial thinking of what may have motivated the person, but of course they are not 100 percent sure that the person is absolutely the responsible person.
"Every day New Zealanders get up in the morning and go to work, or to visit Government departments, and their families expect them to return home. In this case that has not happened and my thoughts are with the loved ones of those who have lost their lives."
Cunliffe begins with minute's silence
David Cunliffe's Christchurch campaign started with a minute's silence for the two people killed in a shooting at an Ashburton Work and Income office.
The Labour leader is in Christchurch to announce the 100 million dollar rail plan for Canterbury and deliver labours promises to the Christchurch community.