A violent clash between police and protesters led to a double amputee getting blasted with pepper spray, but video of the incident shows cops did not take his prosthetic legs as well.

Witnesses say the young man was unarmed and non-violent when he got pepper-sprayed by Columbus, OH police officers Sunday, but footage shows he threw items at cops ... like a sign and a bottle of liquid.

The guy reportedly crawled on his hands to get medical help, but the video shows protesters almost immediately gathered around him to drag him away ... which caused him to lose his prosthetic legs. The legs can be seen disconnected on the ground near him in the video.

More video of the protests shows Columbus cops using their bikes as battering rams to attack the crowd, which is in stark contrast to Mayor Andrew Ginther's statement earlier in the week.

The Mayor said police could deal with violent protesters, but "those on the other side who are truly peaceful, who are truly non-violent, who are truly non-aggressive need to have the space and deserve to have the space to exercise their First Amendment rights, and we should embrace that." The Mayor and City Council also banned the use of peppery spray against non-violent protesters.

So, why the violent clash with peaceful demonstrators Sunday? The Mayor seemed to justify it by saying cops tried for more than an hour to clear the streets, but "they were met with violence from some and took action, including using mace and pepper spray as appropriate to keep crowds in sidewalks."

We've reached out to the police ... we're told they're investigating the incident.