Anonymous wrote:You need a better coop. Hardware cloth, including digging down with a HC floor.
We lost many chickens to a fox, and I do NOT think that is your likely predator. A fox will typically steal one at a time. If you had a single event where all your animals were killed, I would guess raccoon. They are the only ones who seem to kill the whole flock for fun. ESP if the heads were ripped off, not to be too graphic for you urban folks!
OP here. I really appreciate all the comments and advice, particularly regarding making a safer living environment for future birds (based on all this advice, I'm thinking we should stick with chickens). We had five chickens - four were dragged away (never found them), one was left dead in the coop. It was awful. Only good thing is that I found them before my children did. We will definitely make all the necessary security upgrades before we get any new birds. I doubt I can kill the foxes, which seem to roam all over the neighborhood.