A security guard who was caught on video knocking a man out of his wheelchair at a Vancouver mall has been charged with assault.

In October, three undercover security guards at the Pacific Centre Mall were seen surrounding the one-legged man who was suspected of shoplifting.

The scene was captured in a shaky cell phone video obtained by CBC News.

In the video, one of the guards starts swearing before knocking the man out of his wheelchair with a blow to the head.

"I'll f--kin' throw you on the ground and f--k you up!" the guard is heard saying. "Don't f--k with me ... On the ground! On the ground! On the ground! You're so stupid — on your chest!"

Ali Rahnumah, who had been honoured as the "loss prevention officer of the year" in 2011 by Downtown Vancouver's Business Improvement Association, was fired by his employer, Genesis Security, shortly after CBC aired the video.

"He had done well and I was surprised," said Ashley Meehan, vice-president at Genesis Security Group.

"It's not in line with what we expect of our employees. So why it came to that I can't explain."

Rahnumah challenges dismissal

CBC has learned that Rahnumah, 30, is now suing Genesis Security for $25,000 for wrongful dismissal.

In a wrongful dismissal suit filed in small claims court, Rahnumah alleges his firing was "malicious, reprehensible" and designed "to minimize the negative publicity" resulting from the release of the video.

Rahnumah also claims his actions during the arrest were "wholly consistent with the manner in which employees [of Genesis] … acted in the performance of their duties."

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CBC News obtained video of another violent takedown by private undercover security guards at Vancouver's Pacific Centre Mall. (CBC)

The Ministry of Justice conducted its own investigation following reports on CBC News and found one guard used unnecessary force and profanity contrary to the Security Services Regulations' code of conduct.

His security worker license was suspended during the investigation and he received an additional two-month suspension, according to Ministry of Justice spokesman Sam MacLeod. He was also fined $230.

Rahnumah is expected to make his first court appearance in May.

with files from CBC's Eric Rankin