Preface: I love moose. One of my favourite animals, after turtles.
But relax. The animal had an injured foot, he would have been a goner in the wild. He would have limped around, begun slowly starving to death as his mobility decreased and infection set in, eventually collapsing, succumbing to the lack of energy and disease. He'd be lucky to have a top predator come along before the ravens started picking at his still-live body. Nature's a *****.
So, you tell me. If you were in the moose's position, would you pick euthanization, or be relocated, still injured, and endure what I described above. Because I'm sure the City doesn't have the resources to send the moose to the hospital.