A witness who videotaped the death of a Polish man at Vancouver International Airport is suing the RCMP for the return of the footage.

Paul Pritchard filmed Robert Dziekanski's actions "in the minutes before police arrived, the use of the Taser by police, and the 'incredibly shocking' moment the witnesses realized they had just seen a man die," says a statement by his lawyer.

Pritchard agreed to lend the RCMP his camera and the high-quality footage. But now they won't return his property because they say the video may taint witness accounts in their investigation.

"We've withheld the evidence in this very important case that we want to try to get to the truth and to the bottom of," RCMP spokesperson Dale Carr told CTV News in Vancouver.

Carr said police have not ruled out a criminal investigation into the case.

"It's an investigation that is undetermined at this time, and we're just not prepared to make any assertions as to what the outcome is going to be until it's a full and thorough investigation," he said.

Pritchard claims the RCMP promised they would make a copy of the tape before giving everything back to him within 48 hours.

Instead, he received a call stating that the footage would not be returned.

"I'm upset they've gone back on their word and are trying to keep my video from coming out," said Pritchard.

Dziekanski died after a confrontation with police while he was held in a secure area of the airport earlier this month. At one point, police used a Taser stun gun to subdue the man.

A preliminary autopsy report on Dziekanski showed he had no signs of trauma, disease, or any other indicators that would lead to an obvious cause of death.

Police are still looking into how and why the Polish immigrant died, and how he spent the 10 hours between his arrival in Canada and his death.

Pritchard, an ESL teacher returning from China, continued taping the incident even after a guard told him to stop. He then hid the camera in his bag, fearing it would be confiscated. Later, he decided to hand over the footage to police.

Victoria lawyer Paul Pearson has agreed to help Pritchard get his footage back.

"It wasn't seized with a warrant or any other sort of authority, my client lent it to them with the agreement that it would be returned within 48 hours," Pearson told CTV.ca on Tuesday.

"Certainly, our position is, if you lend someone something they have a responsibility to give it back -- it doesn't take a lawyer to tell you that."

Pearson said RCMP officials told Pritchard that he may eventually have the footage returned but that it could take as long as two-and-a-half years.

Murray Mollard of the B.C. Civil Liberties Association says the failure to return the footage may further erode the public's confidence in police.

"Whether the intent or the effect of this kind of going back on an agreement is such that I think people will worry and wonder and be skeptical about the police's motives in this," Mollard said.

Pritchard's lawyer filed a lawsuit in British Columbia Supreme Court last Thursday, and plans to apply for a judge's order to return the video before the end of the week.

"When I saw Mr. Dziekanski's mother crying on television, I knew I had to get that video back and make sure the public gets an accurate picture of how this happened," said Pritchard.

He plans to release the full video to the media if he gets it back.

Another witness, Sima Ashrafinia, captured grainy video of the incident using her cellphone camera. She described Dziekanski as shaking, sweating and "shouting back" at police.

B.C.'s chief coroner has announced an inquest into the death.

With a report from CTV British Columbia