x2 on electric! Electrified poultry netting is great, or multiple strands of hot tape or wire. Premier1supplies.com is a great resource for products and information, online, on the phone, and catalog. Mary
I also think fox or coyote. Whoever it is, return visits are guaranteed, so I hope your birds are in a safe place right now, and everything is reinforced tomorrow. Live traps might help, and/ or a game cam. Good luck, Mary