Is that an "old work" box that has ears that stick out? It doesn't really matter. You're going to have a patch. Cut around the box with a drywall saw and then you'll find out what the deal is. I've put screws in the back of a box in a pinch.

I'm not sure what that even means - "old work" or "ears." Yeah, I guess cutting it out might be the only option - there aren't any screws visible in the back - at lest, not visible from the front.

Youve removed the screws for the ears. check further in the box and see if someone used a couple sheet rock screws to screw it to a stud.

otherwise, yeah, cut the drywall around it and rip it out. should be easy.

When you tug on it you should be able to feel wheres theres no resistance. look there for an extra screw.

An old work box allows a box to be placed anywhere a hole can be cut. A screw at each end actuates a plastic ear that flips out and grabs the drywall. You could use a putty knife to try and move those ears back (although with the screw removed they should have fallen off), but really a 4" x 6" hole is just as easy to patch as a 2" x 4" hole.

Are you sure that none of those wires is still connected somewhere. You might want to get them tested before you start pulling. A whole lot of wires still in that box, and if one is hot, you sure dont want it dropped down inside your wall.

Those plastic electrical boxes have "cable clamps" -- really just plastic tabs -- that prevent wires from being pulled out of the box. Perhaps its the wires running through the clamps that are preventing you from removing the box. I'd try bending the cable clamps upward (or breaking them off) and see whether you can then pull out the box.

Yes, it has to be the cable clamps holding onto the wire

Thank you all! It turns out it was glued or epoxied in!

There were no flaps or ears anywhere. Just the adhesive stuff.

The ears would have fallen off in the wall when you removed the screws.

The issue for me is not the problem with getting the box out, though fortunately you accomplished that. The main concern is the wires remaining in the wall. According to code, you can't just do a sheetrock repair and cap and bury those wires unless they are disconnected at the other end. I agree with cat_ky: how do you know those wires aren't part of a live circuit elsewhere.

How does one go about “disconnecting them at the other end0?

Most of those wires seem like small low voltage wires. Were they controls for the skylight? What's at the end of the white wire? Seems like it was a DIY special.

Yes, they were controls for the skylight. They were here when I moved in over 20 years ago.

Carrie-

1) Not all of those wires are low voltage.

2) You disconnect them at the other end by tracing the wires back to their source. Since I suspect this is beyond your skill level, you need to have an electrician do this if you want a safe and legal result.

Looks like it was on an outside wall and someone tried to use spray foam to keep out drafts.

You can ring the wires and see if the conductors are connected or not.

Thanks, all! No, not an outside wall. Will reach out to my electrician. Thank you!