A police recording of a call made by an RCMP officer after he fatally shot a young man he had arrested was played at a coroner's inquest Wednesday in northern B.C.

Tears welled up in Const. Paul Koester's eyes as the jury listened to about five minutes of the audiotape, including his call for help after he shot 22-year-old Ian Bush of Houston, 300 kilometres west of Prince George.

"Oh no, no, please, oh help me. No, no. Send an ambulance. Can you help me?" Koester says in an anguished voice.

While the tape is of poor quality, Koester can be heard to say, "Oh God, this isn't happening," and something about "in the interview room."

Koester had only been in Houston for five months before the shooting.

On Tuesday, the first day of the inquest into Bush's death, the inquiry was told Bush, a mill worker who died in police custody in Houston in 2005, was shot in the back of the head by an RCMP officer.

Bush was arrested while holding a beer outside a hockey game on Oct. 29, 2005.

He was taken into custody after giving Koester a false name, and 20 minutes later, he was dead.

Koester told the inquiry that he felt he was in a fight for his life when he shot Bush.

He said Bush attacked him in the interview room, striking him repeatedly and eventually pinning him in a chokehold.

Koester said Bush told him "take your last breath."

The officer told the inquiry that he thought he was going to be killed and pulled out his gun. But Koester said he does not remember pulling the trigger.

An internal RCMP investigation determined that Koester fired in justifiable self-defence during a violent struggle, and he was not charged.

B.C. Attorney General Wally Oppal has publicly defended the decision not to charge the officer.

"He feared at that time for his life," Oppal said. "That's the evidence we have. That's the only evidence we have."

Koester is among 20 witnesses scheduled to testify at the inquest this week at the Houston community hall.

The coroner does not assign fault or blame, but rather conducts a fact-finding investigation.

An inquest aims to classify a death as natural, accidental, suicide, homicide or undetermined, and possibly make recommendations aimed at preventing similar incidents.

With files from the Canadian Press