This happened a few weeks ago in San Antonio, TX.
From the video description:
"I was getting ready for work when I spotted a car at a dead end road removing collars from within the car. I put my shoes on quickly and ran out to the road and started recording the act. I am tired of people doing this continuously in the area. I recorded to educated and advise them to do the right thing. The woman in the video responded back for directions to the Animal Care services, and yet decided to commit the illegal activity as directed by driver who then backed out and back seat passenger flipped me off." (credit: YouTube)
Scroll down the page. The story has a happy ending.
The suspects eventually turned themselves in.