Police were called to the store in Great South Rd, Takanini, at 1.10pm yesterday after a panic alarm activation. They found two people dead at the back of the premises.
Last night a police cordon surrounded the Ezy Cash loan shop, where the bodies were expected to remain overnight. Road blocks were due to remain in place between Taka St and Glenora Rd while a scene investigation took place.
Wally Thompson, one of the last people to see one of the victims, described a store worker, aged in his 50s, as "a great guy".
"He was just so helpful."
He went to Ezy Cash just an hour before the tragedy, but left because he didn't have the documents he needed. When he returned about 2.30pm, he found police surrounding the scene.
Police interviewed him and another couple also in the shop before the incident. They told the trio they were among the last to see one of the victims alive.
"My interview with the police was like being in a movie. They were being honest with us and they said 'there's two people in there that were stabbed'."
Despite the danger, he wished he had been in the shop when the incident happened. "If that happened I would've done something to help him. I couldn't let that happen."
Paris Evans, 14, was next door at Super Cheap Auto with friends when the stabbings occurred.
He said he had been told a suspicious van had been parked outside.
"We couldn't believe this happened. It's pretty sad."
Police were appealing for sightings of a Maori or Pacific Island man aged in his 20s and a woman, whose description was not known.
The pair were seen leaving the shop just before police arrived.
"We are in the very early stages of the investigation and currently have very limited knowledge of what occurred at the scene," said Lynch.
"Police need to identify and speak to these two people to ascertain whether they have any information relating to the incident."
Police refused to confirm how the pair were killed, or what weapon was used.
The victims had yet to be identified, but police believed they worked at the store.
Anyone with information should call Counties Manukau police on (09) 261 1300 or Crimestoppers 0800 555 111.