Undercover officer Sgt Don Wilkinson said he was "running, running" after a police lookout told him to get away from the place where he and a colleague had been planting a tracking device, a court heard today.

Sgt Wilkinson was killed and his colleague shot three times while planting the device on a car in South Auckland on September 11 last year.

Iain Lindsay Clegg, 35 and John Ward Skinner, 37 have been jointly accused of Mr Wilkinson's murder and the attempted murder of another undercover officer whose identity is suppressed.

Detective Steven Hare was part of the surveillance group acting as back-up for Sgt Wilkinson and a second officer who has name suppression while the pair attempted to plant the tracking device on John Skinner's car.

Mr Hare told a depositions hearing in Manukau District Court this morning that he had heard a third undercover officer acting as a lookout say over the radio: "Get out of there".

The reply from Sgt Wilkinson was "running, running", but when Detective Sergeant Greg Holmes asked the undercover agent whether the back-up should move in, the reply from the lookout was "no".

When Sgt Wilkinson and his colleague advised they had reached their car on Earlsworth Avenue, Mr Hare asked Mr Holmes if he should get them and was told he should.

Mr Hare said he and his police partner drove several times up and down Earlsworth Avenue with their lights and siren on to try to find the missing pair.

He told the court he saw Mr Holmes parked in the middle of the road and waving them down.

"At that point I saw Sgt Wilkinson and [his colleague] were lying on the ground," Mr Hare said.

He said his partner ran to Sgt Wilkinson and attempted to find his pulse, while he spoke with the second officer to see if he was injured.

Defence Graeme Newell asked "what about Sgt Wilkinson".

Showing obvious emotion, Mr Hare replied "there was no response".

An airgun expert earlier told the court Sgt Wilkinson's death was believed to be the first in New Zealand caused by an airgun.

Ronald Ghen Young, the owner of Young's Air Gun Centre in Mt Roskill, is the biggest retailer of airguns in the North Island.

He sold an FX Monsoon rifle to Mr Skinner last June for $2100. Under cross-examination by Skinner's lawyer, Kevin Brosnahan, Mr Young said that the Monsoon rifle was at the "elite" end of the market.

Under further questioning from Mr Clegg's lawyer Stuart Grieve QC asked Mr Young – who has been in the business for 25 years – if he'd ever heard of another airgun fatality.

He answered: "No, I believe this is the first."