Big bird thats black

Am a bit worried about this bird. We spotted it just sitting on the grass in front of our house. Strange behaviour. So maybe it's hurt? I walked towards it (camera in hand, obviously) and it slowly just walks away from me. I got it into someone elses from garden, inbetween rose bushes. I am concerned because we have 2 cats, plus Harold, and next door has Scampi - who is a a big hunter. Not sure if we'll see the bird again.