Injured bird...anything we can do?

My daughter is talking to a friend who has been working at an animal hospital and she said there's nothing we can do and the bird's leg is pointed completely the wrong way. She said short of killing it myself, just put it outside and leave it to nature, which I think is what we'll do.

Apparently it's a European Sterling which I was told is an invasive species. So...oh well. Bummer.
That’s what I noticed from the photo you posted.
It may have been attacked by a neighborhood feline.
Left outside a night predator of some sort will likely finish the job.