Const. Paul Koester was acting in self-defence when he shot a man in custody at a Houston, B.C., RCMP detachment two years ago, the RCMP Public Complaints Commissioner ruled Thursday.

On Oct. 29, 2005, Ian Bush, a 22-year-old mill worker, was arrested outside a local hockey rink for having an open beer and giving a false name to officers. Twenty minutes later he was shot by Koester, who says the man was choking him from behind.

In a report released Thursday, Commissioner Paul Kennedy cleared Koester of any wrongdoing when he shot Bush while in the process of releasing him from custody.

Kennedy said he came to the conclusion that Koester had acted in self-defence after reviewing information including the coroner's inquest, the communication logs from before and after the incident and physical evidence of a struggle.

"All those things put together led me to conclude that in this case there was a very tragic thing. A minor incident somehow went off track, resulting in the death of an individual," Kennedy told CTV Newsnet on Thursday from Vancouver.

Bush's family says they were disappointed with Kennedy's conclusion.

"The more we see of the investigation -- of the evidence -- it just reinforces our belief that, no, that is not how it happened," said Linda Bush, Ian's mother.

Koester testified that he shot the young man in the back of his head while the two were alone in an interview room. He said Bush had attacked him and that he acted in self-defence.

A blood-splatter expert hired by Bush's family said at the inquiry that the incident could not have occurred the way Koester said it had.

Kennedy said that Bush -- who was under the influence of alcohol -- was asked to sign a note promising to appear in court to face charges of obstruction for giving police a false name, his first criminal charge.

"You have a young gentleman, faced now with something more serious than he had encountered before, intoxicated, and something triggered a violent response that resulted in an attack on the officer," Kennedy said.

At a press conference following the release of the report, Assistant Commissioner Al Macintyre said they found the use of lethal force to be necessary to ensure the officer's safety.

"Const. Koester had a reasonable apprehension of death and believed he could not otherwise preserve himself from death other than to use lethal force," Macintyre said.

A review was launched into Bush's arrest and death in September 2006, as well as a review into how the RCMP handled their following investigation.

The Mounties were criticized for having their own officers investigate the controversial incident. A coroner's inquest was told earlier this year that Koester wasn't formally interviewed for three months after the death.

But Kennedy's review ruled that the North District Major Crime Unit held an accurate investigation within an appropriate time frame.

"The investigation into Mr. Bush's death was conducted in a timely manner and free from any manner of conflict of interest, bias or partiality," Kennedy said in the report.

He told Newsnet that the "level of accountability" was very high in the investigation and that suggestions that Koester received preferential treatment were incorrect.

The report touched on several recommendations, including the installation of closed circuit video equipment in RCMP detachments -- a suggestion also made during the coroner's inquest into Bush's death.

Macintyre said Thursday the installations were underway and should be completed by the fall of 2008, with a cost of $5.5 million to establish the network in B.C. sites alone.

Other recommendations in the report touched on officer field training and the need for policy guiding on-scene RCMP members investigating the actions of other officers and the development of a communication strategy on police-involved shootings.

The New Westminster Police Service and Crown Counsel did their own reviews into the incident, and their findings were concurrent with the CPC's, he said.

"None of the recommendations made by the CPC would have prevented the tragic event that occurred on October 29th, 2005. We recognize at that that what occurred was emotionally difficult for all those involved," said Macintyre.

Macintyre told reporters on Thursday that Koester -- now stationed at a general duty RCMP detachment in the interior of B.C. -- had been sent some "disturbing email"

"He's been getting some rather extraordinary e-mail over the last while," Macintyre said, describing the correspondence as "very derogatory and accusatory of him."

"A citizen has been sending him some rather upsetting and disturbing email and we're going to get to the bottom of that as well."

The Bush family says it will proceed with a civil lawsuit against the RCMP, the B.C. solicitor general and attorney general. The family has said they were disappointed and wanted better recruitment and training for officers.