What are you using for wire? I'd make sure you use a wire with small enough openings and check for any small gaps in the coop. Make sure you lock the chickens up early, too. Even a small delay is enough time for an early predator to come out and get in the coop.
I have all openings in the coop like windows and vents covered in heavy gauge 1/2" hardware cloth. This keeps out the smallest species of weasel and rats. It also keeps racoons from reaching through and killing chickens through the wire.
The rest of the coop is wood. It's put together with wood screws, so it can't be pulled apart. Hardware, like hinges and latches, are also attached with screws instead of nails, so they aren't pulled out. Latches should be the type that aren't easily opened by racoons.
Electric wire and a good dog can help, too.