This happened in downtown Vancouver, and luckily, worried bystanders shot this video and sent it to the local SPCA. The dog, a pit bull, was barking while its owner argued with a cyclist. Witnesses say the dog had lunged at the cyclist ... possibly at the behest of the owner.

But, watch ... after the argument ended, the owner picked up the helpless dog -- above his shoulders -- and threw it down on the concrete sidewalk. The dog yelped and was clearly distressed.

You can hear the horrified witnesses, who immediately called police. Officers reportedly arrested the owner, but later released him without charging him. However, an investigation is still ongoing. It's unclear if police have seen this video.