Updated

British police apologized Wednesday for using a stun gun to subdue a blind stroke victim they wrongly thought was carrying a samurai sword, a bizarre case of mistaken identity that left the man fearing for his life.

Colin Farmer told British broadcasters that he thought he was going to die after he heard a commotion, felt electricity surge through his body, and was knocked to the floor by an unknown assailant. The incident occurred in the town of Chorley, in northern England's Lancashire County, on Friday.

"This seemed to be going on forever ... I was convinced I was being murdered in plain sight," the 61-year-old told Sky News television. "He (the officer) jumped on the small of my back with his knees ... wrenched my arms up my back and cuffed me so tightly I was in great pain." Farmer told the BBC he was shouting: "I'm blind! I'm blind!"

Lancashire Police Chief Stuart Williams said police brought the victim to a local hospital to be checked out after they realized they had used the weapon against the wrong man.

He said in a statement that police "deeply regret" the incident, which happened after police received multiple reports that a man was walking through Chorley "armed with a samurai sword."

Williams said that an urgent investigation had been launched into the incident and that the matter would also be reviewed by the Independent Police Complaints Commission, Britain's police watchdog agency.

Police said a different man was arrested in connection with the sword reports, but was released without charge.

Britain's tough weapons laws severely restrict the possession of blades, knives and knuckle dusters.