People have been putting unwanted puppies and kittens in sacks and throwing them in the river for as long as we've had sacks. It sucks but that's life. Millions of unwanted dogs and cats are destroyed around the world every year. Here in Spain, strays end up in "pounds" which are widely referred to as killing stations. They are starved for a couple weeks cause feeding them costs money, and then gassed... by the government.
There are many animal societies, independently run animal shelters supported by donations with no kill policies, and they usually have 300-400 animals each at any given time, and even they end up having to put them down when they can't find them homes and run out of funds.
What I find most disturbing about this is her jovial attitude in going about disposing of these dogs and the fact they taped it. "Oh boy, we get to kill puppies today! Grab your camera! Weeee...". Do what you have to do but making a fun game out of it shows serious mental issues.