That is a very sad situation. But having him put to sleep is the kindest solution. He’s a danger to people and the neighborhood pets. Feral cats never trully warm up to people and frankly, I’m sure the cat isn’t very healthy and it sounds like he had a very hard life. You obviously can’t keep him caged for the rest of his life either. It’s so sad, If he wasn’t so aggresive he’d make a great barn cat . Sorry you have to to go through this, but you did the right thing in capturing him. *hugs*