The police in Ashburton say they have located what they believe is the gun used in Monday's shooting at the town's Work and Income Office.
They have thanked the public for coming forward with information on the shooting and appealed for others to contact them if they have information about the incident.
48 year-old John Tully has been charged with murdering Peggy Noble and Leigh Cleveland and the attempted murder of Lindy Curtis, who remains in Christchurch Hospital.
The victims were shot at their work place on Monday morning.
Earlier it was revealed that the movements of the man responsible for the shootings were caught on a business CCTV camera and handed to investigators.
ElectraServe is on the corner of Cass and Moore Street, across the road from the Work and Income office.
General manager Blair Watson said the camera captured a man biking to the office, looking through the windows and then leaving on his bike a short time after.
Mr Watson said staff realised within minutes the footage would have been recorded and gave it to the police.
John Tully has been charged with two counts of murder and one of attempted murder. He did not plea when he appeared in the Christchurch District Court yesterday and was remanded in custody to reappear on 23 September.