Hi Jana, I'm new here as well. This is my first post actually. First, sorry for your loss. I have turkeys as well and was wondering what breed your flock was. It is highly unlikely an animal would scare the whole flock and by the description you provided, this sounds like the works of a coon. They can get in any loose place. You have a chain link pen with a nylon net cover? I would add hardware cloth or 2 layers of chicken wire to the fence. Coons will stick their grubby hands through a fence and break the necks of every bird just for the fun of it. They also could have squeezed in somewhere along the top, attacked and killed every bird, and then left the same way they entered. Good luck to you!
~Josh
~Josh