I thought it was obvious it was Ward, and felt Agent 33 telling it to Morse was the writters being like "yes he killed his dog, now stop thinking he'll be redeemed".Ward's dog was intentionally left vague. This was not.
That's a huge red flag that you probably want to get in front of if you can.
Also, I think my brother mostly does it because it bothers me a bit. >.< He thinks it's funny.