This is by no means a Denver only phenomenon. Cops have been shooting dogs in record numbers over the past few years. Most of the time they have no knock warrants, kick down the wrong door, and immediately shoot any dogs in the house because they are a "threat to officer saftey". After they realize they are at the wrong house they give an insincere "sorry" to the family and go on their merry way with no reprecussions for their actions what so ever. Remember a police officer's primary responsibility is making it home to their family safe and sound, your rights, and those of your loved ones/pets are a distant second.
If you really want to get upset, go on youtube and search for "cop shoots dog". Unfortunately there are a ton of videos, and they all make me very sad/angry