Have spotted an injured fox, what's the best thing to do?

We live in a semi-rural area and have foxes coming around usually at night seeking food which we leave out and I'm sure so do some of our neighbours. On Thursday lunchtime I happened to glance out of the kitchen window and spotted a single fox looking for food which I thought very unusual as I thought they were nocturnal animals, however, next early afternoon I spotted him again but this time I noticed he was struggling to walk as his front left paw was being held suspended but I don't know if he's sprained or fractured it. So, what's the best thing to do? Try to catch it and take it to the vet or, put it down to one of nature's casualties?